quantifying periglacial erosion in the nepal high himalaya abstract quantifying erosion rates in high mountain environments is challenging because the erosional processes are often stochastic and catastrophic distinguishing between periglacial and glacial rates is especially challenging in this study we focus on determining erosion rates from a glaciated alpine landscape where the bedrock sidewalls are eroding predominantly by blockfall we utilize a topographically well constrained debris covered glacier on the north slope of the annapurna range central nepal himalaya to quantify an average headwall retreat rate by measuring supraglacial debris depths from 0 1 to 2 4 m and average short term down valley transport rates of 17 m yr we calculate a yearly sediment flux of 5820 1990 m3 yr the supraglacial debris originates from the steep rocky headwall of the valley and we use the calculated flux with an estimated headwall contributing area to determine a slope perpendicular headwall retreat rate of 1 3 0 5 mm yr which corresponds to a vertical lowering rate of 0 42 0 16 mm yr and a horizontal retreat rate of 1 2 0 5 mm yr this rate is significantly greater than the steady state erosion rates that we determine for the valley ridge crests and sidewalls 0 08 0 03 mm yr and 0 20 0 05 mm yr respectively using concentrations of the in situ produced cosmogenic radionuclide 10be additionally 10be exposure ages of the lateral moraine crests and supraglacial debris suggest a glacial advance about 470 yr ago and a long term supraglacial transport rate of about 10 m yr using this long term transport rate reduces our inferred headwall retreat and suggests that the up glacial bedrock slopes are eroding at roughly the same rate while our results do not quantify the rate of glacial erosion the absence of a glacial gorge suggests that there may be a rough balance between glacial downcutting and the erosion of the valley sidewalls rates quantified here are almost an order of magnitude lower than fluvial incision rates of the upper marsyandi river that drains the study area suggesting that even glaciated catchments are not keeping pace with the rapidly down cutting rivers of the himalaya

sediment dates with implications for the age of the conversion from palaeochannel to modern fluvial activity on the murray river and tributaries abstract dates for sediment deposition have been obtained for a number of abandoned channels with modern features on the upper murray kiewa ovens and goulburn rivers and from palaeochannel deposits on the upper murray river just west of albury the dates from modern channels on the upper murray are problematic but suggest modern fluvial activity had begun by 5 9 ka two dates from the ovens and kiewa rivers are in agreement with this west of albury a palaeochannel point bar returned an age of 7 4 11 6 ka and a source bordering sand dune 22 5 ka sand beneath the floodplain near albury was aged 7 3 ka and was not deposited at the same time as underlying gravels where two embedded trees returned ages of 12 ka it therefore cannot be established if the sand deposit was associated with either modern or palaeochannel activity therefore on the upper murray river the transition from palaeochannel to modern fluvial activity most likely occurred between 7 and 10 ka in contrast two dates from an abandoned channel on the goulburn river indicates that modern channels were active on this river before 11 13 ka this suggests that palaeochannels were active later on the upper murray than on the goulburn river and compared with previous work possibly later than on the murrumbidgee river and the middle murray river near echuca as upper catchment areas were revegetated following the lgm discharge or sediment supply may have declined first in lower altitude catchments like the goulburn and last in the high altitude upper murray catchment creating an asynchronous transition from palaeochannel to modern fluvial activity in subcatchments of the southeast murray drainage basin

late quaternary climates of the australian arid zone a review abstract aridity in australia has generally been associated with glacial intervals of the last few glacial cycles the causes and nature of aridity varied from north to south over the continent in northern and central australia reduced monsoon rain in global cold stages caused lakes and rivers to dry vegetation to become more sparse sand dunes to become active and dust advection to increase while the monsoon is correlated with warmer global temperatures and high sea levels overall the exact timing of the greatest development of the monsoon in stage 5 remains uncertain in southeastern australia the proxy records give a less clear picture while vegetation seems to have been more sparse in cold stages and sand dune activity and dust flux consequently greater records of runoff in rivers and lakes have mixed or opposite behaviour to northern or central australia the nature of aridity in southeastern australia is not analogous to conditions anywhere on the continent today greatly reduced temperatures over the central and southern interior greater influence of snow and periglaciation on runoff high groundwater tables lower rainfall and reduced atmospheric carbon dioxide levels may all have contributed to and interacted to produce the reconstructed picture of a cold sparsely vegetated arid landscape with large rivers and perennial lakes the largest changes in circulation patterns over the glacial cycle probably occurred in the location and or intensity of summer tropical convergence in northern australia over southern australia changes to the temperature and humidity of the westerly circulation have been more significant than the small fluctuations in latitude of the sub tropical high pressure ridge

palaeoclimatological and chronological implications of the vostok core dust record the2 083 m vostok ice core recovered by the soviet antarctic expeditions has provided much information of climatic and environmental interest for a period covering a full glacial inter glacial cycle1 6 here we present and discuss the dust record obtained down to 2 202 m the final depth to which this core was extended in 1986 first we document the fact that major changes in aeolian deposits as recorded in the vostok core appear to be of global significance and confirm the existence of a link between high latitude aeolian deposits and the earth s orbital parameters7 8 second we propose atmospheric dust as a strati graphic marker to compare timing with other records of palaeocli mate and use the magnetic susceptibility profile measured along the rc11 120 indian ocean core9 for this purpose assuming that major dust events correspond to common aeolian inputs this approach indicates that the vostok and marine records were roughly in phase at the previous glacial interglacial transition

climatic records over the past 30 ka from temperate australia a synthesis from the oz intimate workgroup temperate australia sits between the heat engine of the tropics and the cold southern ocean encompassing a range of rainfall regimes and falling under the influence of different climatic drivers despite this heterogeneity broad scale trends in climatic and environmental change are evident over the past 30 ka during the early glacial period 30 22 ka and the last glacial maximum 22 18 ka climate was relatively cool across the entire temperate zone and there was an expansion of grasslands and increased fluvial activity in regionally important murray darling basin the temperate region at this time appears to be dominated by expanded sea ice in the southern ocean forcing a northerly shift in the position of the oceanic fronts and a concomitant influx of cold water along the southeast including tasmania and southwest australian coasts the deglacial period 18 12 ka was characterised by glacial recession and eventual disappearance resulting from an increase in temperature deduced from terrestrial records while there is some evidence for climatic reversals e g the antarctic cold reversal in high resolution marine sediment cores through this period the high spatial density of holocene terrestrial records reveals an overall expansion of sclerophyll woodland and rainforest taxa across the temperate region after 12 ka presumably in response to increasing temperature while hydrological records reveal spatially heterogeneous hydro climatic trends patterns after 6 ka suggest higher frequency climatic variability that possibly reflects the onset of large scale climate variability caused by the el nino southern oscillation

proglacial lacustrine sediments from el altar ecuador evidence for late holocene climatic change late holocene glacier variations on el altar ecuador have been reconstructed from proglacial lacustrine sediments variations in bulk density and organic content in sediment cores from laguna verde are interpreted as representing a record of the neoglacial activity of the obsipo glacier two sedimentological units of laminated silt and clay represent two late holocene episodes of glacier expansion which probably occurred during the last millennium and tentatively suggest a double little ice age signal reconstructed equilibrium line altitudes on the obispo glacier seem to reflect changes in both precipitation and temperature and the glacial fluctuations documented on el altar are consistent with other evidence of environmental change from northern south america

valley formation by fluvial and glacial erosion cross valley profiles from the west slope of the olympic peninsula washington are used to investigate the relative effects of fluvial and glacial erosion on valley formation unlike most ranges where glaciers and rivers sequentially occupied the same valleys neighboring valleys in the olympic mountains developed in similar lithologies but were subject to different degrees of glaciation allowing comparison of the net effect of glacial and fluvial processes integrated over many glacial cycles upslope drainage area was used to normalize comparisons of valley width ridge crest to valley bottom relief and valley cross sectional area as measures of net differences in the mass of rock excavated from below ridgelines for 131 valley spanning transects valley width relief and cross sectional areas are similar for glaciated partly glaciated and unglaciated fluvial valleys with drainage areas of 10 km 2 but diverge downslope glaciated valleys draining 50 km 2 reach two to four times the cross sectional area and have to 500 m greater relief than comparable fluvial valleys partly glaciated valleys have intermediate dimensions at distances of 5 km from valley heads the cumulative upstream volume of rock removed to form valleys is two to four times greater in glacially incised valleys than in fluvial valleys the finding of strong differences in the net result of valley excavation by fluvial and glacial erosion supports the interpretation that alpine glaciers are more effective erosional agents than are rivers and implies that large alpine valleys deepened and enlarged in response to pleistocene glaciation

buffers barriers and blankets the dis connectivity of catchment scale sediment cascades abstract catchment configuration and the nature of connectivity within and between landscape compartments affect the operation of sediment cascades and geomorphic responses to disturbance events of differing magnitude and frequency this paper introduces the concept of landform impediments termed buffers barriers and blankets that impede sediment conveyance by limiting the connectivity between landscape compartments buffers restrict sediment delivery to channels barriers inhibit sediment movement along channels and blankets drape channel or floodplain surfaces affecting the accessibility of sediment to entrainment these features operate as a series of switches which turn on off processes of sediment delivery determining the effective catchment area at any given time using previously documented examples the role of these features in affecting the operation of sediment cascades in a low relief passive landscape setting such as the australian landmass is contrasted to examples from high relief uplifting settings in new zealand the australian examples are further explored by examining how changes to landscape connectivity brought about by human disturbance since european settlement have impacted upon landscape sensitivity and prospects for river recovery this approach to analysis of impediments to sediment conveyance is generic and can be applied in any environmental setting

late cenozoic uplift of mountain ranges and global climate change chicken or egg the high altitudes of most mountain ranges have commonly been ascribed to late cenozoic uplift without reference to when crustal thickening and other tectonic processes occurred deep incision and recent denudation of these mountain ranges abundant late cenozoic coarse sediment near them and palaeobotanical evidence for warmer climates where high mountain climates today are relatively cold have traditionally been interpreted as evidence for recent uplift an alternative cause of these phenomena is late cenozoic global climate change towards lower temperatures increased alpine glaciation a stormier climate and perturbations to humidity vegetative cover and precipitation

some geological implications of average quaternary glacial conditions analyses of quaternary landscape evolution tend to focus on events associated with culminations of glacial and interglacial ages but for most of quaternary time environments were intermediate in character average quaternary glacial conditions based on assessment of the marine isotope record approximated those near the stage 2 stage 1 transition and during substages 5b and 5d isotope stages 3 and 4 and substages 5a d lie within one standard deviation of the mean value under average glacial conditions ice sheets lying over northern north america and europe were much more contracted than their full glacial counterparts and the distribution of mountain glaciers reflected a snowline depression of some 500 m geomorphic processes operating under average quaternary conditions contributed importantly to landscape evolution examples of landscapes that may represent such average conditions include cirques and fluvial deposits of the pacific northwest the fjords and strandflat of western norway and atolls of the tropical oceans by examining the geologic record from the perspective of average conditions rather than those of climatic extremes added insight can be gained regarding the evolution of quaternary landscapes

anabranching rivers their cause character and classification anabranching rivers consist of multiple channels separated by vegetated semi permanent alluvial islands excised from existing floodplain or formed by within channel or deltaic accretion these rivers occupy a wide range of environments from low to high energy however their existence has never been adequately explained they occur concurrently with other types of channel pattern although specific requirements include a flood dominated flow regime and banks that are resistant to erosion with some systems characterized by mechanisms to block or constrict channels thereby triggering avulsion the fundamental advantage of an anabranching river is that by constructing a semi permanent system of multiple channels it can concentrate stream flow and maximize bed sediment transport work per unit area of the bed under conditions where there is little or no opportunity to increase gradient on the basis of stream energy sediment size and morphological characteristics six types of anabranching river are recognized types 1 3 are lower energy and types 4 6 are higher energy systems type 1 are cohesive sediment rivers commonly termed anastomosing with low w d ratio channels that exhibit little or no lateral migration they are divisible into three subtypes based on vegetative and sedimentary environment type 2 are sand dominated island forming rivers and type 3 are mixed load laterally active meandering rivers type 4 are sand dominated ridge forming rivers characterized by long parallel channel dividing ridges type 5 are gravel dominated laterally active systems that interface between meandering and braiding in mountainous regions type 6 are gravel dominated stable systems that occur as non migrating channels in small relatively steep basins anabranching rivers represent a relatively uncommon but widespread and distinctive group that because of particular sedimentary energy gradient and other hydraulic conditions operate most effectively as a system of multiple channels separated by vegetated floodplain islands or alluvial ridges

dramatic reduction in size of the lowland macquarie river in response to late quaternary climate driven hydrologic change palaeochannels of lowland rivers provide a means of investigating the sensitivity of river response to climate driven hydrologic change about 80 palaeochannels of the lower macquarie river of southeastern australia record the evolution of this distributive fluvial system six macquarie palaeochannels were dated by single grain optically stimulated luminescence the largest of the palaeochannels quombothoo median age 54 ka was on average 284 m wide 12 times wider than the modern river 24 m and with 21 times greater meander wavelength palaeo discharge then declined resulting in a younger narrower group of palaeochannels bibbijibbery 125 m wide 34 ka billybingbone 92 m 20 ka milmiland 112 m 22 ka and mundadoo 86 m 5 6 ka yet these channels were still much larger than the modern river and were continuous downstream to the confluence with the barwon darling river at 5 5 ka a further decrease in river discharge led to the formation of the narrow modern river the ecologically important macquarie marshes and marra creek palaeochannel 31 m 2 1 ka and diminished sediment delivery to the barwon darling river as palaeo discharge fell further the hydrologic changes suggest precipitation was a driving forcing on catchment discharge in addition to a temperature driven runoff response

downstream hydraulic geometry of rivers in victoria australia abstract downstream variation of hydraulic geometry in rivers characterized by fine textured banks and low width to depth ratios 7 25 is investigated in victoria australia with the aim of developing predictive models of channel geometry for large scale spatial modeling applications a one dimensional hydraulic model is used to determine the mean bank full geometry and discharge q bf for 93 sites which are investigated in relation to discharge of fixed average recurrence interval ari the median bank full ari is estimated at 0 8 years with 75 of sites between 0 5 and 2 5 years exponents in the downstream hydraulic geometry relations for width depth and velocity are respectively 0 43 0 40 and 0 18 q q bf and 0 44 0 38 and 0 03 q q 2 i e 2 year ari falling near the mode of global values q 2 and slope explain 66 of variance in q bf while q 2 explains 73 and 69 of the variance in width and depth relations respectively q 2 provides a reliable substitute for q bf in spatial modeling applications spatial variation in hydraulic geometry relations within and between river basins remains largely unexplained the w d ratio characteristically decreases with increasing distance along the lower reaches of most rivers and this has contributed to the lower than expected value for the width exponent

estimates of late holocene soil production and erosion in the snowy mountains australia soil production in actively uplifting or high precipitation alpine landscapes is potentially rapid however these same landscapes are also susceptible to erosion and can be sensitive to changes in climate and anthropogenic activity which can upset the balance between soil production and erosion the snowy mountains southeastern australia are a tectonically stable low relief moderate precipitation mountain environment the alpine area is extensively blanketed by soil that has been subjected to more intensive episodes of erosion during past periods of anthropogenic disturbance and under cold climate conditions of the late quaternary in this study rates of soil development and hillslope erosion were investigated using radiocarbon dating fallout radionuclides and sediment cores collected from lakes and reservoirs estimated holocene soil development rates were 20 220 t km y erosion rates determined from the radionuclides cs and pb were equivocal due to the inherent spatial variability of radionuclide inventories relative to apparent erosion rates estimated average erosion rates over the past 100 years determined from pb inventories were 60 t km y 95 ci 10 90 inventories of cs observed at the same site implied that more recent erosion rates over the past 60 years was below the detection limits of the sampling method applied here i e 70 t km y the upper estimate of 90 t km y is comparable to the mean erosion rate estimated using the radionuclide method for uncultivated sites in australia and is significantly lower than that measured at sites were vegetation cover was disturbed by livestock grazing prior to its exclusion from the alpine area in the 1940s ce low erosion and high soil production rates relative to the lowland soils are likely related to extensive vegetation cover which in this context protects soils against erosion and contributes to the formation of organic alpine soils that rapidly accumulate organic matter by comparison to other soil types

quaternary fluvial systems of tropics major issues and status of research abstract fluvial systems in tropical regions are not only the lifeline for modern civilizations there but also form an important continental archive for reconstructing quaternary palaeoclimates and palaeoenvironments tropical rivers drain through a variety of geological and geomorphological settings across the world and have been studied for their hydrology sediment transport characteristics facies models stratigraphic development and flood hazards this paper presents an overview of the research on tropical rivers globally and identifies major gaps and unanswered research questions as a part of the igcp 582 on tropical rivers the participants of this project are continuing to tackle many of these issues the collection of papers in this special issue is an outcome of this activity and presents new data on processes and alluvial stratigraphy of the tropical rivers from china india south america and northern australia

morphology hydrology and evolution of the anastomosing ovens and king rivers victoria australia anastomosing channels form the characteristic stream pattern of the riverine plain of southeastern australia investigations of the ovens and king rivers in northeastern victoria show that the individual channels and reaches of channels vary markedly in channel morphology and age young channels have large bankfull flows low sinuosity large meander wavelength steep gradients and are unstable they are incised channels that are rapidly eroding their bed and banks old channels however have small bankfull flows high sinuosity small meander wavelength gentler gradients and are relatively stable the multiple channels develop by avulsion as individual channels become older and more sinuous they also become more hydraulically inefficient thus increasing proportions of flood discharge are displaced overbank this overbank flow concentrates in relatively straight flood plain depressions and it erodes a new channel which develops by both up and down valley incision down valley incision is initiated at outflow points and up valley incision is initiated where the overbank flow rejoins the main channel with time both channel segments join to form a new anabranch of the anastomosing channel system large anastomosing channel networks have been identified in ancient rocks by stratigraphers and sedimentologists on the basis of studies of the anastomosing ovens and king rivers it is very likely that these channel networks are composed of channels of different ages hence even at one stratigraphic level not all of the anabranches functioned simultaneously nevertheless as a result of anabranch incision which intersects older channels at depth a three dimensional network of paleochannels can form that permits fluid flow throughout the network

proglacial lake sediment records reveal holocene climate changes in the venezuelan andes lake sediment records from the cordillera de merida in the northern venezuelan andes document the history of local glacial variability and climate changes during the holocene w12 ka to the present the valleys that contain these lakes have similar bedrock compositions and hypsometries but have different headwall elevations and aspects which makes them useful for investigating the magnitude of past glaciations there was widespread glacial retreat in the venezuelan andes during the early holocene after which most watersheds remained ice free and thus far only valleys with headwalls higher than w4400 m asl contain evidence of glaciation during the last w10 ka there was a pronounced shift in sediment composition for the montos headwall w4750 m asl and los anteojos headwall w4400 m asl records during the middle holocene from w8 0 to 7 7 ka when conditions appear to have become ice free and drier there is tentative evidence that the glacier in the mucubaji valley headwall w4609 m asl advanced from w8 1 to 6 6 ka and then retreated during the latter stages of the middle holocene clastic sediment accumulation in other nearby lake basins was either low or decreased throughout most of the middle holocene as watersheds stabilized under warmer and or drier conditions in the montos record there was another major shift in sediment composition that occurred from w6 5 to 5 7 ka similar to other regional records that suggest conditions were drier during this period overall the late holocene was a period of warmer and wetter conditions with ice extent at a minimum in the northern tropical andes there were also punctuated decadal to multi centennial periods of higher clastic sediment accumulation during the last w4 ka likely in response to periods of cooling and or local precipitation changes in watersheds with headwalls above 4600 m asl there is evidence of glacial advances during the little ice age w0 6e0 1 ka the pattern of glacial variability is generally similar in both the northern and southern tropics during the little ice age suggesting that ice margins in both regions were responding to colder and wetter conditions during the latest holocene the observed pattern of holocene climate variability in the venezuelan andes cannot be explained by insolation forcing alone and tropical ocean influences were likely associated with the observed glacial and lake level changes

rupture of veined granite in polyaxial compression insights from three dimensional discrete element method modeling granite formations have been frequently involved in subsurface energy related activities such as radioactive waste disposal oil and gas storage this is principally because of their mechanical stability low permeability and high corrosion resistance these favorable properties however can be compromised by the addition of mineral veins which tend to occur ubiquitously in upper crustal rock formations evaluation of the impact of veins on the integrity and rupture characteristics of granite especially under true triaxial stresses is therefore important yet currently underemphasized this study examines the rupture of veined granite in polyaxial compression via a discrete element method model in the model with soft veins the rupture is localized along the fabricated inclined veins 45 relative to the horizontal with strike running in the 2 direction under low confining stresses 2 67 mpa in contrast a combined rupture of veins and granite matrix is observed when 2 is increased to 141 6 mpa shear sliding along the inclined veins is revealed by examining the displacement field shear induced volumetric dilation is suspected in the soft veined models in relatively low confining stresses 2 67 mpa with sliding and dilation behavior apparently suppressed at 2 141 6 mpa hard veins impede local rupture resulting in conjugate shear bands the well recognized 2 effect is observed for the hard veined models while no pronounced 2 effect is noticed for the soft veined models this study also reveals that vein thickness has a negligible impact on rupture characteristics which is however profoundly affected by vein orientation

quaternary climatic instability in south east australia from a multi proxy speleothem record milankovitch scale quaternary climatic oscillations within south east australia are known to be characterized by relatively arid glacial and wet interglacial stages however terrestrial proxy records of environmental change are scarce based largely on river terraces dune sediments and pollen sequences here we present a speleothem based palaeoclimate record from yarrangobilly caves south east australia the oxygen isotopic composition of calcite 18ocalcite is taken to represent rainfall amount and used as an aridity index high resolution trace element profiles and uv fluorescence support interpretations based on 18ocalcite allowing further designation of key phases of speleothem growth into periods of relative aridity and moisture excess a hiatus of approximately 37 ka duration divides the record into two key phases of growth which can be mapped onto marine isotope stages 5c a and 3 respectively increasing aridity in the latter half of mis 5 led to cessation of speleothem growth for the duration of mis 4 growth recommences during mis 3 associated with greater moisture availability enhanced vegetation and augmented biogeochemical cycling this speleothem record provides a unique context of terrestrial environmental change and depicts hydrological conditions which fluctuate markedly over the 70 ka period covering the time of megafauna extinction and human arrival on the continent

contemporary geomorphological activity throughout the proglacial area of an alpine catchment abstract quantification of contemporary geomorphological activity is a fundamental prerequisite for predicting the effects of future earth surface process and landscape development changes however there is a lack of high resolution spatial and temporal data on geomorphological activity within alpine catchments which are especially sensitive to climate change human impacts and which are amongst the most dynamic landscapes on earth this study used data from repeated laser scanning to identify and quantify the distribution of contemporary sediment sources and the intensity of geomorphological activity within the lower part of a glaciated alpine catchment odenwinkelkees central austria spatially geomorphological activity was discriminated by substrate class activity decreased in both areal extent and intensity with distance from the glacier becoming progressively more restricted to the fluvially dominated valley floor temporally geomorphological activity was identified on annual seasonal weekly and daily timescales activity became more extensive with increasing study duration but more intense over shorter timescales thereby demonstrating the importance of temporary storage of sediment within the catchment the mean volume of material moved within the proglacial zone was 4400 m 3 yr 1 which suggests a net surface lowering of 34 mm yr 1 in this part of the catchment we extrapolate a minimum of 4 8 mm yr 1 net surface lowering across the whole catchment these surface lowering values are approximately twice those calculated elsewhere from contemporary measurements of suspended sediment flux and of rates calculated from the geological record perhaps because we measure total geomorphological activity within the catchment rather than overall efflux of material repeated geomorphological surveying therefore appears to mitigate the problems of hydrological studies underestimating sediment fluxes on decadal annual time scales further development of the approach outlined in this study will enable the quantification of geomorphological activity alpine terrain stability and persistence of landforms

permeability enhancements of borehole outburst cavitation in outburst prone coal seams abstract borehole outbursts eject coal power create cavities and relieve in situ stress while drilling cross measure boreholes into outburst coal seams for pre drainage this paper highlights the borehole outburst cavitation to enhance the permeability of coal for the first time borehole outburst is a mechanical behavior and the outburst trigger and development depend on the status of gas pressure gradient near the opening coal wall it was testified that the high pressure water with 10 15 mpa in pressure and 20 30 m3 h in flow was feasible to remove the failure coal near the opening wall and stimulate a new set of outbursts thus creating bigger cavities and better permeability enhancement furthermore an outburst control system was designed for borehole outburst cavitation the system contains an outburst stimulation subsystem a gas drainage subsystem and a separation subsystem thus ensuring the flow and the separation of outburst ejections within a relatively closed environment the outburst cavity reconstitutes the in situ stress and permeability of the surrounding coal mass leading to a failure zone a plastic zone and a visco elastic zone the failure zone and the plastic zone due to borehole outburst cavitation are both effective in permeability enhancement finally a field test in the no 10 coal seam at the luling mine proved that the sufficient permeability enhancement scope is approximately twelve times of the cavity radius the permeability enhancement promotes the increase of borehole distance from 5 m to 12 m thus reducing 78 7 of boreholes in number for the pre drainage of the no 10 coal seam

measurement of equivalent doses in quartz from contemporary water lain sediments using optically stimulated luminescence the single aliquot technique and its derivatives are very attractive for the measurement of the very small doses found in young materials because they inherently avoid concerns about low dose non linearity and can offer high precisions a modification is outlined to the single aliquot regeneration and added dose sara protocol mejdahl and botter jensen 1994 quaternary geochronology quaternary science reviews 13 551 5541 to permit its application to sedimentary quartz using the optically stimulated luminescence signal this revised protocol is then used to determine the doses found in several contemporary fluvial sediments and one coastal beach sand thought to be deposi ted by recent wave action two over bank river deposits were both homogeneously well bleached with doses of 0 4 gy although most of the grains in three channel deposits from a range of catchment sizes were also well bleached contamination by a small proportion of very poorly bleached quartz grains prevented the measurement of the dose in the majority the beach deposit was homogeneously bleached and contained a dose of about 0 02 gy it is concluded that over bank sites may provide accurate dates for samples older than a few hundred years but that the heterogeneity of the channel sites limits the accuracy of dates less than a few thousand years

palaeohydrology of lowland rivers in the murray darling basin australia abstract this study derives a new function describing the relationship of channel bankfull discharge qbf to channel width in modern rivers of the murray darling basin mdb of southeastern australia and applies this to dated palaeochannels of seven rivers to quantify late quaternary discharge history in this important basin all rivers show high mis3 and mis2 qbf declining in the holocene the qbf of modern mdb rivers is correlated with total catchment precipitation but comparison with palaeochannel qbf estimates shows that while enhanced runoff efficiency is necessary to account for much larger late pleistocene palaeochannels either lower or higher precipitation rates could have prevailed a strong association between relative palaeo qbf enhancement and temperature suggests a temperature mediated mechanism controlling river discharge such as the fraction of precipitation stored as snow and thawing in spring the enhancement of orographic rainfall or co2 feedbacks with vegetation cover significantly enhanced mis3 qbf requires an additional mechanism such as increased rainfall these findings are consistent with others that increased moisture availability was associated with past colder climates although this was not necessarily the result of enhanced precipitation

three dimensional hoek brown strength criterion for rocks a great number of rock strength criteria have been proposed over the past decades of these different strength criteria the hoek brown strength criterion has been used most widely because 1 it has been developed specifically for rock materials and rock masses 2 its input parameters can be determined from routine unconfined compression tests mineralogical examination and discontinuity characterization and 3 it has been applied for over 20 years by practitioners in rock engineering and has been applied successfully to a wide range of intact and fractured rock types the hoek brown strength criterion however does not take account of the influence of the intermediate principal stress although much evidence has been accumulating to indicate that the intermediate principal stress does influence the rock strength in many instances in this paper a three dimensional 3d version of the hoek brown strength criterion has been proposed the original hoek brown strength criterion is just a two dimensional 2d version of the proposed 3d strength criterion the 3d strength criterion not only inherits the advantages of the original hoek brown strength criterion but can take account of the influence of the intermediate principal stress polyaxial or true triaxial compression test data of intact rocks and jointed rock masses has been collected from the published literature and used to validate the proposed 3d hoek brown strength criterion predictions of the proposed 3d hoek brown strength criterion are in good agreement with the test data for a range of different rock types the proposed 3d hoek brown strength criterion is also compared with a simplified 3d hoek brown strength criterion proposed by pan and hudson the pan hudson criterion cannot be considered a true 3d version of the hoek brown criterion because it does not reduce to the form of the original hoek brown criterion at either triaxial or biaxial state the pan hudson criterion underpredicts the strength at the triaxial state but overpredicts the strength at the biaxial state

proglacial lake sediment records of holocene climate change in the western cordillera of peru abstract sediment records from proglacial lakes between 9 and 10 s in the western cordillera of the peruvian andes document the waxing and waning of alpine glaciers since the end of the lateglacial stage these records from the southern tropical andes provide supporting evidence that the early holocene between 12 and 8 ka was relatively warm and dry and the middle holocene between 8 and 4 ka was marked by a shift to cooler and possibly wetter conditions in certain regions leading to glacial advances although there were multiple periods of brief ice advances that interrupted the overall trend glaciers in multiple valleys generally retreated from 4 0 ka through the medieval climate anomaly 1 0 0 7 ka this late holocene pattern of ice retreat occurred during a period when lake level studies and both lacustrine and speleothem stable isotopic records indicate wetter conditions relative to the middle holocene suggesting that higher temperatures contributed to the pattern of ice retreat following this period of glacial retreat multiple proxy records suggest that the start of the little ice age 0 6 0 1 ka was a colder and wetter time throughout much of the tropical andes there appear to be two primary synoptic scale climatic controls on temperature and precipitation linked to insolation dynamics that drive changes in ice cover in the southern tropical andes during the holocene 1 the strength of the south america summer monsoon which is linked to northern hemisphere temperatures and the mean position of the intertropical convergence zone over the atlantic and 2 sea surface temperature distributions in the tropical pacific ocean and its influence on atmospheric temperature precipitation and circulation patterns

gas emission prediction and recovery in underground coal mines abstract strata gas can be released and captured from non active and active gas resources either from virgin or relaxed strata both prior to and when mining activities take place the high and irregular gas emissions associated with high production longwall mining have provided a need to optimise the methods used to predict these gas levels and the ventilation requirements for gas dilution a forecast of gas emissions during development drivage and longwall mining indicated possible gas and ventilation problems requiring the introduction of various gas drainage techniques and in maintaining the necessary air quantities in ventilation systems to satisfy the statutory gas limitations for various coal production rates although there are sound principles used in world recognised methods of gas emission prediction a new approach developed from long term practical experience in underground gassy coal mine practices and gas rock mechanics studies appear most suitable for local conditions and mining systems in use the lunagas floorgas and roofgas geomechanical and gas emission models offer an effective solution to these problems both programs are the most advanced engineering numerical tools available to calculate gas source contributions to total gassiness and improve the accuracy and quality of gas control gas capture technologies and ventilation system design

tl chronology and stratigraphy of riverine source bordering sand dunes near wagga wagga new south wales australia abstract riverine source bordering dunes are found throughout the murray basin of southeastern australia at the eastern and northern margins of late quaternary palaeochannels the dunes are dominated by locally derived sand but often contain a minor calcareous clay component originating from a distant westerly source in the bedrock confined valley of the murrumbidgee river near wagga wagga the dunes occur as discrete mounds on the floodplain or as drapes over the marginal valley side slopes tl dating of three stratigraphic units within the dunes shows that phases of sand accumulation occurred between 15 and 25 ka in oxygen isotope stage 2 clarendon unit between 35 and 60 ka in stage 3 glenfield unit and between 80 and 120 ka in stage 5 yarragundry unit the tl ages here which show excellent agreement with those determined respectively for the yanco kerarbury and coleambally phases of palaeochannel activity on the riverine plain j quat sci 11 1996 311 extend the emerging regional model of late quaternary climatic and hydrologic change for southeastern australia

shale claystone response to air and liquid exposure and implications for handling sampling and testing abstract this paper documents the results of scientific studies to quantify the impact on shales and claystones of exposure to air and to different liquids these studies show that the water content of such rocks is controlled by the relative humidity of the surrounding air most shales claystones will lose water shrink and desaturate if exposed to air unless the relative humidity is sufficiently high usually 80 96 causing desiccation damage while exposure to brine will prevent desiccation it results in water uptake and swelling and a different type of alteration and damage confining stress will limit this swelling well preserved shales are generally fully saturated under zero stress conditions but they have a negative pore water pressure hydrocarbon will not normally enter a fully saturated shale based on these findings it is recommended that shale water content should not be altered unless it is done so under controlled conditions to accomplish this one must minimize exposure to air and avoid contact with water or brine unless the shale is under stress specific guidelines are provided for core handling and preservation sampling and testing gas shales are both similar to and different than claystone shales and this alters slightly the findings and guidelines

topographically associated but chronologically disjunct late quaternary floodplains and terraces in a partly confined valley south eastern australia the bellinger river catchment in the new england fold belt on the mid north coast of new south wales is characterized by an assemblage of stepped late quaternary alluvial units late pleistocene terraces were formed by large more competent rivers that eroded almost entire valley floors however a decline in discharge prior to the holocene has resulted in the abandonment of these deposits as elevated terraces or residual alluvium onlapped by contemporary floodplains intrinsic controls on floodplain formation appear to be superimposed over an early mid holocene climatic signature a fluvially active period known as the nambucca phase from 10 to 4 5 ka eroded late pleistocene terraces two floodplain surfaces one higher than the other both started to accrete vertically from 4 ka but with some valley locations remaining vulnerable to episodes of erosion resulting in substantial units of even younger basal alluvium the high floodplain is dominated by horizontally laminated vertically accreted sequences while the low floodplain which overlaps in age is characterized by pronounced cut and fill stratigraphy terraces and floodplains in partly confined settings can have similar elevations but be polycyclic with very different basal ages in such landscapes the classical assumption that individual terrace or floodplain profiles along a valley represent periods of coeval formation is shown to be frequently invalid copyright 2007 john wiley sons ltd

australian dust deposits modern processes and the quaternary record abstract dust raising and transport are common and important processes in australia today the aridity of the australian continent and high climatic variability result in widespread dust raising in the arid and semi arid areas and transport to the humid margins and surrounding oceans the supply of erodible particles appears to be the greatest limitation on total flux of transported dust dust raising is greatest in the lake eyre basin including the simpson desert and murray darling basin where internal drainage renews supplies of fine particles to the arid zone in the west and northwest dust entrainment is low despite considerable aridity the marine record of dust flux shows at least a threefold increase in dust flux compared with the holocene in the last glacial maximum in both tropical and temperate australia driven by weakened australian monsoon rains and drier westerly circulation respectively despite the widespread confirmation of aeolian dust deposits in southeastern and southwestern australia dated or quantified records are extremely rare the dominant model of australian dust deposits the clay rich parna is shown to be poorly substantiated while modern and ancient dust deposits examined in detail are shown to bear a strong similarity to conventional definitions of loess

hydraulic conductivity changes and influencing factors in longwall overburden determined by slug tests in gob gas ventholes abstract this study presents the results of core log analyses from the exploration boreholes the analyses of face advance rates and the results of downhole monitoring studies performed in gob gas ventholes for calculation of changes in hydraulic properties in the longwall overburden at a mine site in southwestern sw pennsylvania section of northern appalachian basin in the first part of the study coal measure rocks in overburden strata were analyzed and the locations where possible fractures and bedding plane separations would occur were evaluated in the second part the hydraulic conductivities were computed by two different slug test analyses methods using the water level changes measured in gob gas ventholes as longwall face approached hydraulic conductivities were analyzed with respect to the changes in overburden depth the locations of the borehole and mine face advance rates these data were used to interpret the potential productivities of the gob gas ventholes as a result of fracturing and changes in hydraulic conductivities the general results showed that the probability of fracturing and bedding plane separations in the overburden increase between strong and weak rock interfaces also the probability of bedding plane separations increases as the interface is close to the extracted coal seam evaluation of slug tests showed that the hydraulic conductivity developments in the boreholes and their potential production performances are affected by the underground strata and the roof materials in situations where the roof material is stiff and thick the development of high permeability fractures around the borehole will be less results also indicated that borehole location with respect to face position affects the fracturing time and permeability evolution as well greater overburden depths generally cause earlier fracturing as longwall face approaches but eventually result in lower hydraulic conductivities and potentially less effective boreholes increasing mining rates also resulted in generally lower hydraulic conductivities in the overburden the results of this study were intended to improve the interpretation of gob gas venthole performance and to provide better siting of these boreholes

evidence for regionally wet conditions before the lgm in southeast australia osl ages from a large palaeochannel in the lachlan valley abstract optically stimulated luminescence osl techniques have been used to obtain the rstages on late pleistocene channels in the lachlan valley southeastern australia two osl ages fromchannel sand and overlying source bordering dune sand indicate that large sinuous channels withbankfulldischargessixtoeighttimesgreaterthanthepresentriver werefullyestablishedby34kabp this conclusion is consistent with regional lake level and geomorphic evidence of cool pluvialconditions that preceded the last glacial maximum lgm providing new information on a long standing palaeohydrological problem caused by the apparent synchroneity of large river systems andregional aridity copyright 2007 john wiley sons ltd keywords late quaternary palaeochannels palaeohydrology quartz osl luminescence dating the late pleistocene environmental history of southeasternaustralia relies to a large extent on the relict rivers lakes anddune elds of the riverine plain occupied today by the murrayriver and its tributaries the goulburn murrumbidgee lachlanand darling rivers which rise on the southeastern highlands during the terminal pleistocene the plains supported large actively meandering channels with scrolled oodplains sub stantially larger and carrying coarser sediment loads thanthe irregularly sinuous and muddy present day channels thegoulburn and murrumbidgee palaeochannels have been wellstudied and chronologies based on radiocarbon and thermo luminescence tl suggest two periods of large meanderingchannel activity from 35ka to 25ka and 20ka to 13ka bowler 1978 bowler et al 1978 schumm 1968 page et al 1991 1996 page and nanson 1996 however the regionalchronology does not clearly reveal two synchronous periodsofactivity table1 andisbedevilledbydatinguncertainties forexample suspected contamination of some radiocarbon datesby younger organic compounds contained in the groundwater bowler 1978 was con rmed when kotupna sedimentsradiocarbon dated at 16 13k

mechanical behaviors and failure processes of precracked specimens under uniaxial compression a perspective from microscopic displacement patterns abstract hydraulic slotting is an efficient permeability enhancement method that has been widely used in china for enhanced coalbed methane ecbm recovery although some research has been conducted on hydraulic slotting the mechanical behaviors such as strength deformation and cracking processes of coal treated by this technique are still unclear this paper numerically investigates the mechanical behaviors of specimens containing combined flaws with various inclination angles research results show that different flaw inclination angles result in variations in strength and deformation of precracked specimens we also analyzed the crack initiation propagation and coalescence processes to understand the underlying mechanisms for the aforementioned variations to evaluate the crack initiation and propagation process and its corresponding mechanisms we proposed 12 types of displacement field modes from the perspective of particles relative motion based on this evolution of the displacement field during loading process is analyzed and 11 types of crack and three types of crack initiation modes are extracted from the cracking processes of specimens with different inclination angles analysis of the displacement field not only indicates the type of each crack but also reveals the formation mechanism of the three crack initiation modes a comparison between the numerical results and the previous laboratory test results shows that numerical simulation can reproduce most of the phenomenon observed in the laboratory test the research result is expected to contribute to the further understanding of the mechanical behavior of coal subjected to hydraulic slotting or the stability of rock structures

palaeomagnetic stratigraphy of lake bungunnia plio pleistocene precursor of aridity in the murray basin southeastern australia abstract the murray darling river system in southeastern australia formerly flowed into a large lake lake bungunnia before reaching the sea fine grained clastics of this system the blanchetown clay formation extend over an area of about 68 000 km2 underlying the mallee region with its surface array of dunes and salt lakes palaeomagnetic analyses are used to date the major hydrologic transition from the expansive freshwater system to the saline deflation playas and dunes that characterize this landscape today two sites were selected for sampling one a cliff section on the left bank of the murray river at chowilla the other from within sediments of lake tyrrell a saline playa cut into sediments of the older freshwater system two sequences were sampled at tyrrell one by coring to 30 m in the basin centre the other a composite cliff and 5 m core on the western margin of the playa post bungunnia sediments representing modern landforms were sampled in both surficial dune palaeosol units of the woorinen formation and in saline sediments the tyrrell beds within the modern saline playa the sequence of multiple aeolian units of the woorinen formation and gypseous sediments of the tyrrell beds are normally magnetized indicating deposition within the past 0 7 million years by contrast the uppermost horizons of bedded blanchetown clay below a surface zone of pedogenic alteration are reversed the brunhes matuyama b m boundary key to the age of draining of lake bungunnia by deepening the overflow channel to the sea is obscured within the zone of pedogenesis separating unaltered blanchetown clays from overlying aeolian deposits the onset of aeolian and saline gypseous deposits characteristic of the arid zone facies is placed soon after the b m boundary about 500 000 years ago sequences through the blanchetown clay pass down through the matuyama reversed chron into the gauss normal chron with the lowermost section on the tyrrell west bank recording a basal reversed zone of possible gilbert age thus the origins of lake bungunnia extend back beyond basal pleistocene into the late pliocene the lake s duration covers more than 2 million years spanning the plio pleistocene boundary in this important region of southeastern australia

glacial landscape evolution implications for glacial processes patterns and reconstructions this special issue presents a collection of papers that address a wide range of important challenges and exciting advances in the field of glacial landscape evolution primarily these papers reflect persistent uncertainty that surrounds the mechanisms and timescales of glacial landscape evolution for example estimates of the duration of glacial occupancy required for the evolution of characteristic glacial valley forms from previously fluvial landscapes range from 100 kyrs for landscapes beneath large ice sheets jamieson et al to 400 600 kyrs for glaciated alpine terrains brook et al further the mechanisms of glacial erosion are debated through analyses of the importance of ice thickness brocklehurst et al van der beek and bourbon ice surface steepness vieira and in the case of large ice sheets the co evolution of ice sheet thermal regime dynamics and subglacial topography kleman et al swift et al debate concerning the potential climatic impacts of landscape evolution in alpine terrains is represented by van der beek and bourbon who infer a significant increase in relief as a direct result of glacial erosion and by brocklehurst et al and heimsath and mcglynn who demonstrate respectively that glacial relief production can be surprisingly modest and that rates of glacial erosion may be lower than those for fluvial incision further confirmation that valleys beneath large ice sheets evolve through selective linear erosion comes from studies that have combined geomorphological evidence with cosmogenic nuclide briner et al and apatite u th he thermochronometry swift et al and the resulting style of landscape evolution is demonstrated by the antiquity of fjords in east greenland swift et al and of deep erosion zones and thick drift covered zones in fennoscandia kleman et al although the location of areal scouring zones may be subject to major alteration during single glacial events kleman et al another set of papers shows that analyses of glacial lineation systems continue to provide important data on the dynamics of glacial landscape evolution whether the lineations are formed underneath ice streams bradwell et al andreassen et al or not jansson and glasser and whether they indicate intricate patterns of landscape modification andreassen et al or preservation jansson and glasser the final three papers address rarely reported issues relating to landscapes of glacial deposition including moraine degradation putkonen et al proglacial hydrogeology robinson et al and the evolution of hummocky till topography clayton et al

climatic and vegetation control on sediment dynamics during the last glacial cycle as climate is changing rapidly there is an increasing need to understand how water and soil resources respond to climate change soil and sediment dynamics are sensitive to several external factors such as climate vegetation type and distribution human activity and tectonic activity however the relationship between erosion and changes in these factors is difficult to constrain with current available approaches here we show that uranium isotopes in sediments from river paleochannels can be used to reconstruct variations in the residence time of sediments in a catchment over the past 100 k y we find that sediment residence times increase by an order of magnitude during interglacials compared to glacial periods this is interpreted as a change in sediment stores in the landscape that are tapped by catchment erosion young upland soils during glacial periods reworking of old alluvial sediments during interglacials a direct correlation is found between the sediment residence time and climatic parameters sea surface temperature atmospheric carbon dioxide content and paleorainfall estimates suggesting that during a glacial cycle sediment dynamics closely follow variations in climate however this relationship is not simple because there is no correlation between sediment residence time and paleodischarge estimates because sediment residence time variations correlate with changes in vegetation inferred from pollen data it is hypothesized that the influence of climate on erosion over a glacial cycle may be indirect and operates via the influence of climate on the type of plant ecosystems within a catchment if verified elsewhere this conclusion would emphasize the important role of biology in the physical evolution of earth s surface here observed over a 100 k y time scale

paul mohr coulomb failure criterion for geomaterials abstractpaul mohr coulomb pmc failure criterion provides enhanced representations of pyramidal failure surfaces with recognizable material parameters by considering all three principal stresses

calibration of the c 14 timescale over the past 30 000 years using mass spectrometric u th ages from barbados corals uranium thorium ages obtained by mass spectrometry from corals raised off the island of barbados confirm the high precision of this technique over at least the past 30 000 years comparison of the u th ages with 14c ages obtained on the holocene samples shows that the u th ages are accurate because they accord with the dendrochronological calibration before 9 000 yr bp the 14c ages are systematically younger than the u th ages with a maximum difference of 3 500 yr at 20 000 yrbp the u th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration

alluvium of antiquity polycyclic terraces in a confined bedrock valley confined river valleys are not the localities where long term preservation of alluvium would be expected the 25 km long low gradient 0 0014 m m 1 confined valley setting of the shoalhaven river has archived alluvium of middle pleistocene age to maintain a relatively uniform channel as an efficient conduit for a wide range of flows in a confined bedrock valley of variable morphology single grain optically stimulated luminescence osl dating has identified polycyclic terraces up to 193 ka in age marine isotope stage mis 7 with lower terrace remnants dating from 173 140 ka mis 6 and 106 ka mis 5 holocene alluvium 2 3 5 ka in age caps these old pleistocene units and a well constrained combination of one dimensional and two dimensional hydraulic modelling demonstrates that these polycyclic terraces are clearly within reach of the modern hydrological regime the 106 ka terrace at 17 m above low flow is inundated by floods recurring on average every 20 years and the 140 193 ka terraces at 20 22 m are overtopped every 50 100 years these ancient diachronous landforms exhibit complex depositional histories and are on lapped by longitudinal benches of modern sand and gravel their polycyclic nature appears to be a response to flow reduction using alluvium to adjust the boundary of the otherwise inflexible morphology of a bedrock gorge

factors controlling suspended sediment transport in himalayan glacier meltwaters abstract suspended sediment concentration was determined both on the rising and falling limbs of the flow hydrograph between 28 august and 21 september 1992 and 23 october to 17 november 1993 within a 600 m reach of the dokriani glacier portal ganga basin garhwal himalaya in the ganga basin proglacial stream patterns of sediment flux first follow the spring rise in discharge between april and june then the frequency of occurrence of monsoonal rainstorms has an impact increasing the discharges with high sediment flux between july and mid september and after the cessation of rainfall the discharges are mainly controlled by outflows from subglacial waters coupling sediment with runoff suggests that glacially controlled sediment exhaustion is offset between july and the middle of september by the monsoonal regime and later maintained sediment transfer by the subglacial linked cavity or distributed system

wetting and drying of australia over the past 300 ka alternately dry and wet climatic episodes across central and eastern australia during the past 300 ka have greatly affected australia9s rivers lakes and dune fields evidence of widespread climate and flow regime changes has been provided by 75 thermoluminescence tl dates and 18 u th dates from alluvial and eolian sediments fluvial conditions dominated part of the last two interglacials stage 5 and 7 resulting in large sand loads in rivers in the present simpson desert and southeastern australia during the last interglacial fluvial activity in central australia peaked at 110 ka stage 5 pluvial probably 5 10 ka behind world temperature and sea level maxima following the last late interglacial wet phase aridity associated with dune building spread from central australia toward its margins achieving greatest intensity during the last glacial maximum a less widespread wet phase identified at about 55 35 ka stage 3 subpluvial is associated with high lake levels and paleochannel activity in southeastern australia this tl record of variable continental aridity in australia correlates well with global changes including the variable eolian dust flux into central china the northern pacific ocean and antarctica

stress magnitudes in the basel enhanced geothermal system abstract this paper presents the results of an evaluation of stress magnitudes in the granitic egs reservoir in basel switzerland the profile of minimum principal horizontal stress shmin is constrained by hydraulic tests but the magnitude of the maximum horizontal principal stress shmax is uncertain here we derive estimates for shmax by analysing breakout width data from an acoustic televiewer logs run in the granitic basement section of the bs 1 borehole some 81 of the borehole in the granite is affected by breakouts the approach employed to derive shmax magnitude from the estimated breakout widths is taking into account all stress components at the borehole wall including the remnant thermal stress arising from the cooling of the borehole wall by the drilling in bs 1 breakouts width tends to decrease with depth assuming there is no significant systematic change in the strength characteristics of the rock along the length of the hole for which there is no evidence the large scale trend has the consequence of implying a small gradient of the shmax profile a low shmin gradient was also implied by a stress analysis that additionally considered the occasionally coincident presence of drilling induced tension fractures the absolute values of shmax depend upon the failure criterion used criteria that consider the strengthening effect of the intermediate stress mogi coulomb and hoek brown 3d yield profiles that violate frictional limits on the strength of the crust above 4 km whereas the profiles of the mohr coulomb and rankine criteria do not the mohr coulomb criteria profiles indicate a trend in shmax from favoring strike slip faulting above 4200 m to strike slip normal faulting below this is consistent with focal mechanisms recorded during the reservoir stimulation which show a mix of strike slip and normal faulting throughout the depth range considered

lake bungunnia a plio pleistocene megalake in southern australia abstract between 2 5 ma and 0 7 ma a plio pleistocene megalake lake bungunnia existed in the western murray basin australia study of hydrologic and geologic constraints on this lake has enabled the climate of southeastern australia during the late pliocene and early pleistocene to be partly quantified modelling shows that lake bungunnia could not exist under current climatic conditions and that an average rainfall of at least 500 mm yr 1 over the catchment of the murray darling river system was likely considerably more than at present minor changes in climate caused large fluctuations in the shoreline of the shallow lake which are reflected in the geologic record possible histories for lake bungunnia are suggested in the light of this evidence demise of the megalake heralded the onset of aridity in southern australia and modern landforms date from that time salt lakes in part of the western murray basin may have directly descended from lake bungunnia

coal permeability improving mechanism of multilevel slotting by water jet and application in coal mine gas extraction multilevel slotting by water jet is one of the effective methods used to improve the coal seam permeability as the example of the 1603 working face of guhanshan coalmine first using acoustic emission technology we analyzed the mechanical properties and crack propagation characteristics of the multilevel slotting coal under the condition of uniaxial loading then using the particle flow software pfc2d we numerically simulated the fracture stress and porosity evolutions of the multilevel slotting coal and analyzed the coal permeability improving mechanism of the slot crack network meanwhile the borehole gas extraction slotted by water jet underground was field tested the study found that the coal s body strength could be weakened significantly when the number of slots was increased and the multilevel distribution of the slots induced a great amount of crack growth and extension which formed the slot crack network reduced the stress concentration and increased the coal porosity field tests demonstrated that the gas extraction effect underground was significantly improved the ability of gas extraction of multilevel slotting borehole was enhanced by 5 10 times compared with the conventional borehole and the coal permeability coefficient was increased by about six times

a fully coupled coal deformation and compositional flow model for the control of the pre mining coal seam gas extraction abstract fully coupled compositional coal seam gas and air model of coal deformation coal gas flow and transport and air flow in coal seams is developed to better understand the gas drainage processes and the coal gas air mixing mechanisms during pre mining coal seem gas extraction the model was first verified by showing that the modelled gas concentration profiles match reasonably with the in situ measured ones the verified model was then applied to evaluate how the drained gas concentration could be controlled under different conditions of the sealing length the leakage rate and the leakage fracture width these modelled results provides the basis of a new in situ control technology of gas air mixing which uses fine expansive particles to seal the leakage fractures around the borehole this technology has been commercially applied to enhance the concentration of the pre mining gas drainage the field test shows that the characteristics of the leakage fractures are greatly changed after the particles are injected into the in seam drainage borehole when the gas concentration declines once the leakage fractures are blocked with the particles the outside air is prevented from entering the coal seam thus an ideal gas concentration can be maintained and the duration of higher gas concentration is extended for boreholes with an originally low gas concentration 0 30 the new technology can increase the gas concentration by 10 65 and extend the production time by approximately two to three months the total amount of gas drainage increases to 2000 3000 m 3 per borehole

limiting envelopes of a dry porous limestone under true triaxial stress states abstract the present study investigates the influences of the confining pressure and the intermediate principal stress on the mechanical behaviour of a porous limestone true triaxial tests are carried out on a broad range of confining stresses covering both brittle and ductile regimes the experiments included the special cases of triaxial compression extension and isotropic compression as well as tests at constant levels of the intermediate principal stress the resulting stress strain curves and yield stresses are then discussed three dimensional yield envelopes are subsequently built in meridian and octahedral planes the shape of the octahedral sections changes with the mean stress from triangular to hexagonal and then quasi circular at even higher mean stresses the evolution continues towards a triangle with apexes oriented in the direction of triaxial extension stress states various existing yield criteria are fitted and compared to the experimental data finally a three dimensional yield surface is proposed combining the previous observations

a high resolution late quaternary depositional history and chronology for the southern portion of the lake mungo lunette semi arid australia abstract the willandra lakes region sits on the southern margin of australia s arid core and is one of the oldest localities on the continent known to have been occupied by australia s first people the archaeological traces that accumulated in the lake mungo lunette paint a picture of changing land use over the past 50 thousand years ka and some of these are likely to have been responses to changes in palaeoenvironmental conditions this study set out to determine the finest temporal resolution that can be used to study the depositional and palaeoenvironmental history of the lake mungo lunette the investigation focused on the depositional history documented within stratigraphy exposed in an eroding gully in the southern part of the lunette gully 10 a stratigraphic framework was developed using sedimentological and soil micromorphological analysis this framework was then fixed in time by 56 single grain optically stimulated luminescence osl age estimates these data sets were then combined into a bayesian model that indicated three depositional phases 100 ka lu1 65 33 ka lu2 lu3 and from 30 to 16 ka lu4 lu9 with the late pleistocene and holocene samples lu10 11 not being modelled furthermore the redating of thirteen lower and upper mungo osl samples from bowler et al 2003 s study of the southern tip of the lunette yielded younger age estimates for twelve of these bringing them into line with previously published independent age control as well as the ages presented in this study this study provides an approach for future efforts to establish consistency in age estimation and palaeoenvironmental interpretation along the length of the lunette

contemporary suspended sediment dynamics within two partly glacierized mountain drainage basins in western norway erdalen and bodalen inner nordfjord abstract this paper focuses on environmental controls spatiotemporal variability and rates of contemporary fluvial suspended sediment transport in the neighboring partly glacierized and steep erdalen 79 5 km 2 and bodalen 60 1 km 2 drainage basins in the fjord landscape of the inner nordfjord in western norway field work including extended samplings and measurements was conducted since 2004 in erdalen and since 2008 in bodalen the distinct intra and inter annual temporal variability of suspended sediment transport found is mostly controlled by meteorological events with most suspended sediment transport occurring during pluvial events in autumn september november followed by mostly thermally determined glacier melt in summer july august and by mostly thermally determined snowmelt in spring april june extreme rainfall events 70 mm d 1 in autumn can trigger significant debris flow activity that can cause significant transfers of suspended sediments from ice free surface areas with sedimentary covers into main stream channels and is particularly important for fluvial suspended sediment transport in years with occurring relevant debris flow activity the total annual drainage basin wide suspended sediment yields are strongly determined by these single extreme events the proportion of glacier coverage followed by steepness of slopes and degree of vegetation cover in ice free surface areas with sedimentary covers are the main controls for the detected spatial variability of suspended sediment yields the contemporary sediment supply from glacierized surface areas and the jostedalsbreen ice cap through different defined outlet glaciers shows a high spatial variability the fact that the mean annual suspended sediment yield of bodalen is with 31 3 t km 2 yr 1 almost twice as high as the mean annual suspended sediment yield of erdalen 16 4 t km 2 yr 1 is to a large extent explained by the higher proportion of glacier coverage in bodalen 38 of the drainage basin surface area as compared to erdalen 18 of the drainage basin surface area and by a significantly higher sediment yield from the glacierized area of the bodalen drainage basin compared to the glacierized surface area in erdalen when looking at the total annual mass of suspended sediments being fluvially exported from both entire drainage basin systems the total amount of suspended sediments coming from the ice free drainage basin surface areas altogether dominates over the total amount of suspended sediments coming from the glacierized surface area of both drainage basins drainage basin wide annual suspended sediment yields are rather low when compared with yields of other partly glacierized drainage basin systems in norway and in other cold climate environments worldwide which is mainly due to the high resistance of the predominant gneisses towards glacial erosion and weathering the altogether only small amounts of sediments being available within the entire drainage basin systems the stable and nearly closed vegetation cover in the ice free surface areas with sedimentary covers and the efficiency of proglacial lakes in trapping sediments supplied by defined outlet glaciers both contemporary and long term suspended sediment yields are altogether supply limited contemporary suspended sediment transport accounts for nearly two thirds of the total fluvial transport and accordingly plays an important role within the sedimentary budgets of the entire erdalen and bodalen drainage basins

determination of sealing depth of in seam boreholes for seam gas drainage based on drilling process of a drifter abstract in order to determine a reasonable sealing depth for seam gas drainage boreholes an innovative method is proposed to study the geological conditions in the coal seam by monitoring the response of the drift while drilling the boreholes based on the investigation of the in situ tests on the drift we found that the idle pressure of the hydraulic motor which features a rapid increase at the depth of approximately 14 to 16 m from the roadway wall appeared to be suitable for characterizing the coal mass condition then a numerical simulation was performed to investigate the reason for the response of the idle pressure it reveals that high stress and gas pressure are the main factors accounting for the rapid increase of the idle pressure accordingly the rapid increase of idle pressure becomes an indication for high stress and gas pressure next for determining the sealing depth the gas drainage process with different sealing depths was studied via numerical simulation and a simplified theoretical analysis was conducted to comprehend the flow of air from the roadway to the borehole the analysis reveals that the reasonable sealing depth should be several meters larger than the stress concentration area which is indicated in practice by the idle pressure then a sealing depth of 16 to 18 m is determined for the iii1011 mining face in the haizi coal mine this research provide a real time method to determine the sealing depth for in seam boreholes

comparison of intact rock strength criteria for pragmatic design abstractthis paper compares several intact rock strength criteria against an extensive database comprising 128 data sets with over 7 000 laboratory test results it includes over 1 000 new test data from several recent tunneling projects in australia the database includes sedimentary igneous and metamorphic rocks with unconfined compressive strength ucs values ranging from less than 10 to over 300 mpa the criteria assessed are modified weibols cook lade hoek brown and two of its modifications and christensen several interpretations and conclusions are drawn any of the criteria can provide good fits to test data that do not show much scatter however curve fitting becomes problematic when there is variability in the test data the variation in test data swamps the differences between criteria on balance the hoek brown criterion with its parameters mi and a derived as recommended and extended to three dimensions in the literature where required produces a better fit to the majority of rock t

a failure criterion for rocks and concrete based on the hoek brown criterion abstract there have been a number of attempts at developing three dimensional hoek brown 3d hb failure criteria with non circular cross sections to include the effect of the intermediate principal stress for rocks which is neglected in the classical hb criterion those existing 3d hb criteria predict the same strength as the classical hb criterion in triaxial extension txe and triaxial compression txc this paper presents a new failure criterion for rocks and concrete based on a unified expression of the 3d hb failure criteria which can account for the strength difference between txe and txc the failure cone of the new criterion is convex and smooth everywhere and the deviatoric cross section of the failure cone can cover various shapes from a curved triangle as the lower bound to a circle as the upper bound the deviatoric plane locus is controlled by a shape factor k which can be easily identified from txe tests the proposed failure criterion has been validated by biaxial compression tests of concrete txc txe tests of intact rocks and concrete as well as polyaxial compression pxc tests of intact rocks jointed rock masses and concrete results show that the new 3d criterion with an empirical parameter k 0 99 performs well in characterizing the rock and concrete strength in pxc in the absence of txe test data the application of the new criterion to cross anisotropic rock in pxc is also discussed to show the fabric effect on the rock failure

uranium series isotopes in colloids and suspended sediments timescale for sediment production and transport in the murray darling river system abstract we have measured 238u 234u 230th radioactive disequilibria in five size fractions of colloids and suspended sediments for four rivers from the murray darling river basin se australia continuous compositional trends of composition are observed for 234u 238u and 230th 238u activity ratios over the range of size fractions studied they are explained by the variable contribution of two components detrital alumino silicates and organic matter using relationships between activity ratios and the loss on ignition it is possible to estimate the u series isotopic composition of both detrital and organic end members which provide the best estimate for the composition of the true detrital phase i e controlled only by the removal of elements through weathering and the true dissolved phase i e colloid free respectively when performing a single filtration at 0 2 m it appears that size fractions and

improvement of coal seam gas drainage by under panel cross strata stimulation using highly pressurized gas abstract directed at creating fractures and extracting methane in low permeability high gas outburst coal seams this paper presents the results of a comprehensive integration trial of under panel cross strata drilling with a new coal seam stimulation technique the cardox system in a colliery located in a major high gas content and outburst prone coal field in the central part of china on the basis of the coal seam parametric measurements the precise designation of under panel cross strata borehole patterns and the arrangement of the fracturing and monitoring procedures the advantages of the cardox system in creating fractures and improving gas drainage efficiency of low permeability coal seams are 1 changing the trend of gas concentration and or pure gas quantity over time 2 maintaining the uptrend of gas concentration and or pure gas quantity in a relatively long time period which in the current case is ninety days and counting and 3 elevating gas drainage to a higher level stimulation mechanisms of the highly pressurized gas system have been proposed and based on these mechanisms the crushing and fracturing radii created by the highly pressurized gas have been calculated and corroborated well with the field monitoring data

glacial and deglacial climatic patterns in australia and surrounding regions from 35 000 to 10 000 years ago reconstructed from terrestrial and near shore proxy data abstract this study forms part of a wider investigation of late quaternary environments in the southern hemisphere we here review the terrestrial and near shore proxy data from australia indonesia papua new guinea png new zealand and surrounding oceans during 35 10 ka an interval spanning the lead up to the last glacial maximum lgm the lgm proper 21 2 ka and the ensuing deglaciation sites selected for detailed discussion have a continuous or near continuous sedimentary record for this time interval a stratigraphically consistent chronology and one or more sources of proxy climatic data tropical australia indonesia and png had lgm mean annual temperatures 3 7 c below present values and summer precipitation reduced by at least 30 consistent with a weaker summer monsoon and a northward displacement of the intertropical convergence zone the summer monsoon was re established in northwest australia by 14 ka precipitation in northeast australia was reduced to less than 50 of present values until warmer and wetter conditions resumed at 17 16 ka followed by a second warmer wetter phase at 15 14 ka lgm temperatures were up to 8 c lower than today in mainland southeast australia and up to 4 c cooler in tasmania winter rainfall was much reduced throughout much of southern australia although periodic extreme flood events are evident in the fluvial record glacial advances in southeast australia are dated to 32 2 5 19 1 1 6 and 16 8 1 4 ka with periglacial activity concentrated towards 23 16 ka deglaciation was rapid in the snowy mountains which were ice free by 15 8 ka minimum effective precipitation in southern australia was from 14 to 12 ka in new zealand the glacial advances date to 28 21 5 and 19 ka with the onset of major cooling at 28 ka or well before the lgm there is no convincing evidence for a younger dryas cooling event in or around new zealand but there are signs of the antarctic cold reversal in and around new zealand and off southern australia there remain unresolved discrepancies between the climates inferred from pollen and those inferred from the beetle and chironomid fauna at a number of new zealand sites one explanation may be that pollen provides a generalised regional climatic signal in contrast to the finer local resolution offered by beetles and chironomids sea surface temperatures ssts were up to 5 c cooler during the lgm with rapid warming after 20 ka to attain present values by 15 ka the increase in summer monsoonal precipitation at or before 15 ka reflects higher insolation warmer ssts and steeper thermal gradients between land and sea the postglacial increase in winter rainfall in southern australia is probably related to the southward displacement of the westerlies as ssts around antarctica became warmer and the winter pack ice and antarctic convergence zone retreated to the south

climate of the last glaciation in new zealand based on aerosolic quartz influx in an andesitic terrain abstract on western north island new zealand a record of climatic change during the last glaciation is preserved in a terrestrial coverbed sequence of dominantly andesitic provenance here a succession of five loess like andisol units postdates the global high sea level stand of oxygen isotope substage 5e

how did rivers in the wet tropics ne queensland australia respond to climate changes over the past 30 000 years the nature and timing of fluvial response and coincident changes in climate as inferred from multiple independent proxies are examined in the wet tropics of north eastern australia chronostratigraphic data provide evidence for regionally synchronous fluvial aggradation at 30 13 ka 8 5 ka and again from 1 ka terrace incision and removal occurred at 13 8 ka and 5 1 ka a new synthesis of regional palaeoenvironmental proxy records spanning the last 30 ka highlights key periods of environmental change comparison of the records of fluvial and environmental change reveals the relationship is complex with no clear relationship between river aggradation incision and wetter drier conditions the nature and timing of fluvial response in the wet tropics also shows broad similarities with coastal valleys in south eastern new south wales suggesting continental scale controls on fluvial response to changing climate during the late quaternary in australia copyright c 2017 john wiley sons ltd

mind the gap an absence of valley fill deposits identifying the holocene hypsithermal period of enhanced flow regime in southeastern australia the holocene sedimentary record in southeastern australia is present in a range of landscape settings such as upland swamps dells internally drained lake basins alluvial fans and mid catchmen

calculating quaternary glacial erosion rates in northeast scotland northeast scotland is an area exhibiting selective erosion by quatemary ice sheets in this area both glacial and preglacial landforms exist in close proximity the depths of erosion which this modification represents are calculated on the assumption of various depths of preglacial weathering a depth of erosion of between 34 and 62 m per unit area is indicated calculated rates of erosion are 0 021 nun a for the entire 2 3 m y of the quaternary and between 0 1 and 0 5 mm aa1 on the assumption that glacial conditions existed in this area for 500 000 years and 100 000 years respectively these figures are compared to the offshore sedimentary record in the adjacent west central north sea the volume of sediment deposited offshore is equivalent to a depth of erosion of 195 m per unit area yielding an average erosion rate of 0 085 mm a i over the entire quatemary rates of erosion were low in the preglacial pliocene 0 049 mm a 1 and early quatemary 0 063 mm a the expansion of ice sheets across the area in the middle quatematy was associated with a sharp increase in the rates of erosion 0 13 mm a but the last late devensian ice sheet in the area was less erosive 0 095 mm a the estimated rates of erosion represented by the offshore sedimentary record therefore exceed the estimated rates of glacial erosion from the onsho re geomorphological reconstruction

coal strength and young s modulus related to coal rank compressional velocity and maceral composition abstract this paper presents an experimental investigation of coal rank and maceral composition influences on the coal mechanical behaviors the complete stress strain behavior uniaxial compressive strength young s modulus and acoustic compressional velocity were measured and correlated to coal ranks and microstructures the test results show that coal is an elasto brittle geo material and its uniaxial compressive strength and young s modulus increase as coal rank increases this occurs because as vitrinite reflectance or coal rank increases coal has less microporous structure and thus higher uniaxial compressive strength therefore using vitrinite reflectance value instead of vitrinite content is advantageous for correlating coal strength the experimental results also demonstrate that compressive strength and young s modulus have positive exponential correlation even for different types of coal therefore the compressive strength of coal is highly related to its young s modulus the uniaxial compressive strength and acoustic compressional velocity of coal are also correlated but a single correlation does not exist for different coal ranks instead different relationships occur for different types of coal

improvement of methane drainage in high gassy coal seam using waterjet technique traditional methane drainage methods including conventional ventilation and boreholes drilled in the coal seam are widely used in modern coal mining operation in china however it is often noted that the gas drainage presents low efficiency in most coal mines due to low permeability of the coal seam which not only affects the safety but also the productivity of the coal mine this paper describes the development and application of the waterjet cutting system which is used to create artificial fractures and increase the permeability of coal seam for the improvement of methane drainage in underground coal mines in china according to underground monitoring a significant improvement of methane drainage efficiency of up to 3 to 6 times over the traditional methods has been achieved

clastic sediment flux to tropical andean lakes records of glaciation and soil erosion we developed records of clastic sediment flux to 13 alpine lakes in peru ecuador and bolivia and compared these with independently dated records of regional glaciation our objectives are to determine whether a strong relationship exists between the extent of ice cover in the region and the rate of clastic sediment delivery to alpine lakes and thus whether clastic sediment records serve as reliable proxies for glaciation during the late pleistocene we isolated the clastic component in lake sediment cores by removing the majority of the biogenic and authigenic components from the bulk sediment record and we dated cores by a combination of radiocarbon and tephrochronology in order to partially account for intra basin differences in sediment focusing bedrock erosivity and sediment availability we normalized each record to the weighted mean value of clastic sediment flux for each respective core this enabled the stacking of all 13 lake records to produce a composite record that is generally representative of the tropical andes there is a striking similarity between the composite record of clastic sediment flux and the distribution of 100 cosmogenic radionuclide crn exposure ages for erratics on moraine crests in the central peruvian and northern bolivian andes the extent of ice cover thus appears to be the primary variable controlling the delivery of clastic sediment to alpine lakes in the region which bolsters the increasing use of clastic sediment flux as a proxy for the extent of ice cover in the region the crn moraine record and the stacked lake core composite record together indicate that the expansion of ice cover and concomitant increase in clastic sediment flux began at least 40 ka and the local last glacial maximum llgm culminated between 30 and 20 ka a decline in clastic sediment flux that began 20 ka appears to mark the onset of deglaciation from the llgm at least one millennium prior to significant warming in high latitude regions the interval between 20 and 18 ka was marked by near holocene levels of clastic sediment flux and appears to have been an interval of much reduced ice extent an abrupt increase in clastic sediment flux 18 ka heralded the onset of an interval of expanded ice cover that lasted until 14 ka clastic sediment flux declined thereafter to reach the lowest levels of the entire length of record during the early middle holocene a middle holocene climatic transition is apparent in nearly all records and likely reflects the onset of neoglaciation and or enhanced soil erosion in the tropical andes

lacustrine fluvial interactions in australia s riverine plains climatic forcing of fluvial systems has been a pre occupation of geomorphological studies in australia since the 1940s in the riverine plain southeastern australia the stable tectonic setting and absence of glaciation have combined to produce sediment loads that are amongst the lowest in the world surficial sediments and landforms exceed 140 000 yr in age and geomorphological change recorded in the fluvial fluvio lacustrine and aeolian features have provided a well studied record of quaternary environmental change over the last glacial cycle the region includes the willandra lakes whose distinctive lunette lakes preserve a history of water level variations and ecological change that is the cornerstone of australian quaternary chronostratigraphy the lunette sediments also contain an ancient record of human occupation that includes the earliest human fossils yet found on the australian continent to date the lake level and palaeochannel records in the lachlan willandra system have not been fully integrated making it difficult to establish the regional significance of hydrological change here we compare the willandra lakes environmental record with the morphology and location of fluvial systems in the lower lachlan an ancient channel belt of the lachlan willandra creek acted as the main feeder channel to willandra lakes before channel avulsion caused the lakes to dry out in the late pleistocene electromagnetic surveys geomorphological and sedimentary evidence are used to reconstruct the evolution of the first new channel belt following the avulsion single grain optical dating of floodplain sediments indicates that sedimentation in the new middle billabong palaeochannel had commenced before 18 4 1 1 ka a second avulsion shifted its upper reaches to the location of the present lachlan river by 16 2 0 9 ka the timing of these events is consistent with palaeohydrological records reconstructed from willandra lakes and with the record of palaeochannels on the lachlan river upstream willandra lakes shows high inflows during the last glacial maximum 22 ka but their subsequent drying between 20 5 ka and 19 ka was caused by river avulsion rather than regional aridity this case study highlights the benefits of combining fluvial with lacustrine archives to build complementary records of hydrological change in lowland riverine plains

stratigraphic architecture resulting from late quaternary evolution of the riverine plain south eastern australia the riverine plain of south eastern australia is the result of prolonged cenozoic fluvial activity single thread anabranching and distributary channels and floodplains and associated aeolian dunes characterize the uppermost sequences based on detailed interpretations of late quaternary fluvial sedimentation and surficial stratigraphy for this 77 000 km2 basin earlier prior stream and ancestral stream models of fluvial deposition deduced from limited stratigraphic and chronological evidence are replaced with aggradational palaeochannel and migrational palaeochannel models thermoluminescence dating reveals four distinct phases of palaeochannel activity between 105 and 12 ka the first coleambally phase late in oxygen isotope stage 5 the second kerarbury phase in stage 3 the third gum creek phase before and the fourth yanco phase after the last glacial maximum lgm in stage 2 the first three of these phases were characterized by mixed load laterally migrating sinuous palaeochannels with occasional transitions to a straighter bedload dominated mode and vice versa the first two phases concluded with a bedload dominated episode resulting in aggradational palaeochannels on the surface of the plain and the third phase prior to the lgm did also in its downstream reaches the phase following the lgm was characterized entirely by large mixed load sinuous migrational palaeochannels these exhibited no terminating bedload episode because the onset of holocene climates reduced the size of the flood peaks greatly diminished the supply of bedload from the upper catchments and resulted in streams evolving to their present highly sinuous suspended load form the result is a complex stratigraphic architecture consisting of vertically and laterally accreted units extending over hundreds of kilometres in the form of channel sand stringers sand sheets and derivative aeolian dunes partially or wholly encased in overbank fines

aeolian fluvial interaction and climate change source bordering dune development over the past 100 ka on cooper creek central australia abstract this study provides an interpretation of interrelated quaternary fluvial and aeolian activity related to climate change on cooper creek in the lake eyre basin in southwestern queensland central australia the extensive muddy floodplain is characterised by buried sandy palaeochannels now almost entirely invisible but stratigraphically connected to source bordering dunes that emerge as distinctive sandy islands through the floodplain surface luminescence dating has identified pronounced periods of fluvial activity represented by abundant sandy alluvium from marine isotope stages mis 8 3 while all these sandy fluvial episodes on cooper creek were much more powerful than anything subsequent they appear to be ranked in order of declining activity mis 8 6 saw reworking of almost the entire floodplain whereas subsequent phases of reworking were far less extensive source bordering dunes were derived from active sandy channels in late mis 5 85 80 ka and mid mis 3 50 40 ka after 40 ka sand channel activity largely ceased and the floodplains and channels were inundated with mud isolating the dunes as emergent features although aeolian reworking of the upper parts of some dunes has continued to the present they show remarkable resilience having survived without appreciable migration for at least 40 ka whilst the channels once determined the location of source bordering dunes in an interesting role reversal the remnant dunes now determine the position of many contemporary flood channels and waterholes by deflection and confinement of overbank flows

mass movement in the himalaya new insights and research directions abstract ongoing studies that relate tectonics to the processes at the surface of earth show that many more sources of information about agents of shallow denudation such as mass movement are required to comprehend the long term erosion that leads to deep denudation over geologic time mass movement in the himalaya is scale dependent from the massive extension of whole mountain ranges gravity tectonics through the sackung failure of single peaks to the smallest slope failures generally denudation of the himalayan orogen begins with slope failure onto glaciers and into river valleys and continues by glacial and fluvial transport the maximum size of stable slopes and mean angles of slope that are produced by these failures are complex and controlled by a variety of factors including mass strength of the rocks stress fields angles of internal friction controlled by rock type cohesion that includes the control of rock temperature bulk unit weight of rock and discontinuities the processes of mass movement in the himalaya have been described many times for the past two centuries recently developments in a variety of fields have been introduced to assess the character of mass movement geomorphometry remote sensing digital elevation models and geographic information system technology are revolutionizing the study of mass movement in the himalaya

episodic fluvial activity of inland rivers in southeastern australia palaeochannel systems and terraces of the lachlan river inland rivers in southeastern australia preserve a long record of surface palaeochannels accompanied by alluvial terraces that reflect changes in water and sediment discharges from the southeastern highlands through much of the last glacial cycle a compilation of ages on rivers of the southern murray darling basin together with new dates from the lachlan river suggest that the fluvial response to climate change has been regionally consistent and responsive to climate change on timescales 10 ka for much of the last glacial cycle inland rivers were mixed load sinuous single and anabranching channels that carried bankfull discharges of between 3 and 11 times present day rivers incision of the upper alluvial plains and valleys occurred in the lead up to the coldest part of the last glacial cycle this was followed at 34 ka by the synchronous development of large meandering channels that may have been associated with lower evapotranspiration from alpine highland catchments accompanied by higher precipitation smaller channels and declining lateral channel sedimentation suggests arid climates during the last glacial maximum and late glacial period with seasonally large actively migrating channels being maintained in rivers dominated by snowmelt runoff from the australian alps during the holocene sensitivity to recorded changes in precipitation amounts and variability differed between catchments with some rivers constructing larger or more actively migrating channels in the early to mid holocene

non dilatant deformation and failure mechanism in two long valley caldera rocks under true triaxial compression abstract we conducted laboratory rock strength experiments in two ultra fine grained brittle rocks hornfels and metapelite which together are the major constituent of the long valley caldera california usa basement in the 2025 2996 m depth range both rocks are banded and have very low porosity uniaxial compression tests at different orientations with respect to banding planes reveal that while the hornfels compressive strength is nearly isotropic the metapelite possesses distinct anisotropy conventional triaxial tests in these rocks reveal that their respective strengths in a specific orientation increase approximately linearly with confining pressure true triaxial compression experiments in specimens oriented at a consistent angle to banding in which the magnitudes of the least 3 and the intermediate 2 principal stresses are different but kept constant during testing while the maximum principal stress is increased until failure exhibit a behavior unlike that previously observed in other rocks under similar testing conditions for a given magnitude of 3 compressive strength 1 does not vary significantly in both long valley rock types regardless of the applied 2 suggesting little or no intermediate principal stress effect strains measured in all three principal directions during loading were used to obtain plots of 1 versus volumetric strain these are consistently linear almost to the point of rock failure suggesting no dilatancy the phenomenon was corroborated by sem inspection of failed specimens that showed no microcrack development prior to the emergence of one through going shear failure plane steeply dipping in the 3 direction the strong dependency of compressive strength on the intermediate principal stress in other crystalline rocks was found to be related to microcrack initiation upon dilatancy onset which rises with increased 2 and retards the failure process we infer that strength independence of 2 in the long valley rocks derives directly from their non dilatant deformation

failure properties of cubic granite marble and sandstone specimens under true triaxial stress abstract cubic specimens of granite marble and sandstone with side lengths of 50 mm were prepared in the laboratory true triaxial compression tests were conducted on each rock type with minor principal stress 3 magnitudes of 10 20 30 50 and 100 mpa and the intermediate principal stress 2 varying from 2 3 to 2 1 where 1 represents the major principal stress the experimental results demonstrated that the failure strength fracture dip angle non linear behavior and failure mode of these rocks under true triaxial conditions were affected by both 2 and 3 as well as by the rock lithology when 3 was kept constant and 2 increased failure strength showed an initial increase followed by a decrease whereas the fracture dip angle increased monotonically the non linear behavior before the peak strength point of granite became more apparent by the increase of 3 whereas 2 had an opposite effect on the non linear behavior of granite under high 3 e g 100 mpa the non linear behavior before the peak strength point was always found in marble and sandstone for all of the stress state conditions analyses of fracture dip angle and failure mode showed that when 3 10 20 and 30 mpa and 2 3 5 7 5 and 10 respectively the failure mode of granite changed from shear to slabbing whereas marble and sandstone always fractured in the shear direction this study confirms that rocks may experience slabbing failure under true triaxial stress and slabbing failure mode is likely to be induced in high strength and brittle rocks under low 3 with the stress ratio of 2 3 exceeding a particular threshold value

chronology of murrumbidgee river palaeochannels on the riverine plain southeastern australia four major periods of palaeochannel activity have been identified on the murrumbidgee sector of the riverine plain of southeastern australia on the basis of stratigraphic information the channels reveal a picture of changing flow conditions during the last full glacial cycle the ages of the periods were determined from nearly 40 thermoluminescence dates on surficial fluvial and aeolian sediments these are named the coleambally phase which occurred from 105 to 80 ka the mid to latter part of oxygen isotope stage 5 the kerarbury phase from 55 to 35 ka stage 3 the gum creek phase from 35 to 25 ka late stage 3 to early stage 2 and the yanco phase from 20 to 13 ka late stage 2 the present flow regime was established by about 12 ka stage 1 the first two phases correlate with episodes of enhanced fluvial activity in northern and central australia and with reduced dust activity globally the phases in stage 2 appear to be associated with seasonal snow melt and increased peak flows in periods flanking the last glacial maximum source bordering aeolian dunes associated with the coleambally kerarbury and yanco phases were found however the tl dates show that some have undergone aeolian reworking thermoluminescence dating and fluvial stratigraphy have revealed a detailed picture of late quaternary climate and flow regime changes that has the potential to extend to identified deposits stratigraphically older than those described here

disequilibrium of holocene sediment yield in glaciated british columbia it is generally supposed that specific sediment yield the quantity of sediment passing a monitored river cross section per unit area drained upstream of that section declines as the area drained increases1 3 part of the sediment mobilized from the land surface is supposed to go back into storage at field edges and on footslopes and floodplains in contrast we show here that data from british columbian rivers reveal a pattern of increasing specific sediment yield at all spatial scales up to 3 104 km2 this results from the dominance of secondary remobilization of quaternary sediments along river valleys over primary denudation of the land surface the result controverts the conventional model which has been derived from studies of small highly disturbed agricultural catch ments the rivers are still responding to the last glaciation giving a landscape relaxation time greater than 10 kyr this holds pro found implications for geomorphological theory and for studies of erosion