local scouring at grade control structures in alluvial mountain rivers 1 scour holes below 73 grade control structures check dams and bed sills in six mountain rivers located in the eastern italian alps have been surveyed the most likely formative water discharge is used to evaluate jet thickness at each structure which along with drop height appears to determine scour hole dimensions as shown by the consistent trends observed for nondimensional plots of both maximum scour depth and length versus the respective drop ratio sediment differences regarding size and lithology apparently play a minor role in determining scour hole dimension measured maximum scour depths are well predicted by a semiempirical equation developed through laboratory results showing an average relative error of 0 13 scour hole geometry is described by several ratios that are thought to represent approximately invariant characteristics a new energy based normalization for scour hole dimensions is proposed as the most suited to evaluate the role of jet geometry and aeration upon scouring efficiency it is noteworthy that the ratio between the maximum scour depth and the total energy available at a drop tends toward an asymptotic value around unity for increasing drop heights

effect of sill spacing and sediment size grading on scouring at grade control structures sequences of arti cial steps are sometimes used to reproduce the natural step pool morphology of high gradient streams the depth length and shape of the scour holes in gravel bed rivers can be predicted reasonably using recently developed formulae however the properties of the scour holes can sometimes be affected by the distance between structures this effect is called geometrical interference and leads to a reduction of the scour hole compared to its potential size geometrical interference may occur in sequences of arti cial steps in high gradient torrents where structures are sometimes built at distances of a few tens of metres apart but may also apply to natural step pool systems in this paper a series of tests have been conducted to determine the effect of bed sill spacing and sediment grading on the potential erosion by jets forming over the sills a new formula is derived applicable to high gradient streams slope 0 04 which can be applied to the special case of scour holes developed by interfering sills sediment size gradation not accounted for in previous formulae is found to have a signi cant effect on the scour dimensions and is included in the new predictive formula copyright 2004 john wiley sons ltd

emergence of the canadian rockies and adjacent plains a comparison of physiography between end of laramide time and the present day abstract the landscape of the canadian rockies in southern alberta is not a direct result of constructional processes that is the ridges and peaks have not been pushed into the positions in which we see them today tectonic activity provided original elevation but not mountains at the end of laramide time what are now the front ranges and foothills of the rockies comprised a high elevation upland of relatively low relief the present mountain physiography is the result of 55 60 million years of post orogenic differential erosion in which more resistant rocks have been left at higher elevations than less resistant rocks the canadian rockies and the foothills are developed in a thin skinned thrust and fold belt created during the laramide orogeny the adjacent interior plains cut across foreland basin sediments derived from the mountains the mountains currently consist of large parts of ridges of well indurated paleozoic and locally proterozoic rock alternating with valleys developed in soft mesozoic clastic rock in the foothills where the soft mesozoic rock is at the surface relief is subdued but ridges of more resistant sandstone rise above shaley lowlands the plains are relatively flat but also contain erosional outliers of higher paleo plains surfaces numerous lines of evidence suggest that the mountains and foothills have lost several kilometers of overburden since the end of the laramide orogeny while the western plains have lost at least 2 km requiring that the local relief of the mountains and foothills that we see is erosional in origin local physiography is adjusted to lithology the mountains have high relief because the exposed sub mesozoic rocks can hold up high steep slopes whereas the foothills have low relief because the underlying cretaceous rocks cannot hold up high steep slopes the east facing escarpment at the mountain front is a fault line scarp along a low angle thrust mesozoic rocks involved in the deformation originally extended all the way across the thrust and fold belt and physiography of the belt at the end of laramide time 60 55 ma depended mainly on whether mesozoic or paleozoic proterozoic rocks were exposed at the surface at that time a reconstruction using critical taper theory generally agrees with reconstructions from earlier stratigraphic and paleothermometry studies what are now the front ranges at the eastern edge of the rocky mountains were mostly or perhaps entirely covered with mesozoic rocks and despite that high elevation had a hilly not mountainous character the main ranges in the central rocky mountains were in part stripped of mesozoic cover by then and more mountainous treeline was higher then and the thrust belt may have been largely or entirely vegetated generation of modern relief in the front ranges including the escarpment at the mountain front had to await stripping of mesozoic rocks and incision of rivers into harder substrates in post laramide time the interior plains are an erosional surface that was cut 1 to 3 km below the aggradational top of the foreland basin sediments although some of the present low local relief of the plains results from weakness of underlying cretaceous tertiary rocks the low relief is probably largely related to the process of denudation

calculation of vitrinite reflectance from thermal histories a comparison of some methods vitrinite reflectance values ro calculated from commonly used methods are compared with respect to time invariant temperatures and constant heating rates two monofunctional methods one involving a time temperature index to vitrinite reflectance correlation tti ro and the other involving a log ro to depth correlation yield vitrinite reflectance values that are similar to those calculated by recently published arrhenius based methods such as easy ro the approximate agreement between these methods supports the perception that the easy ro algorithm is the most accurate method for the prediction of vitrinite reflectances throughout the range of organic maturity normally encountered however calibration of the e methods against vitrinite reflectance data from two basin sequences with well documented geologic histories indicates that although the easy ro method has wide applicability it slightly overestimates vitrinite reflectances in strata of low to medium maturity up to a ro value of 0 9 the two monofunctional methods may be more accurate for prediction of vitrinite reflectances in similar sequences of low maturity an older but previously widely accepted tti ro correlation consistently overestimates vitrinite reflectances with respect to other methods underestimation of paleogeothermal gradients in the original calibration of time temperature history to vitrinite reflectance may have introduced a systematic bias to the tti ro correlation used in this method also incorporation of tai thermal alteration index data and its conversion to ro equivalent values may have introduced inaccuracies

affinity and similarity of local scour holes at bed sills 1 excessive erosion of gravel bed rivers represents a hazard which is often controlled by the construction of bed sills shape and volume of equilibrium local scour holes at bed sills in high gradient streams were investigated by analyzing steady flow experimental data scour profiles were normalized by scaling the depths and the longitudinal distance from the upstream sill with the maximum dimensions of the scour hole results exhibited a universal geometrical affinity of the scour geometrical similarity was also found to occur but only in a limited range of physical conditions evidence on the scaling nature of the scour hole shapes has important implications on the prediction of the eroded volume in turn a correct evaluation of the eroded volume is necessary for the optimization of the design of the intersill distance prediction formulae are proposed which link the eroded volume to the geometrical hydraulic and sediment properties

sediment supply and local scouring at bed sills in high gradient streams 1 this paper presents the results of an experimental study about the pattern of local scouring generated at the toe of bed sills which are commonly built in steep gravel bed mountain streams the aim of this study is to evaluate the effect of upstream sediment supply on the scour depth and shape the experiments simulated conditions of a steady upstream sediment supply which had the same grain size composition as the sediment deposit placed on the bed of the flume the geometric characteristics of three scour holes developed under conditions of steady flow discharge and steady upstream sediment supply were measured during 48 different tests this provided a data set containing measurements of 144 scour holes three different sediment feed rates were used and tests were also performed with clear water conditions geometric interference between sills was not observed a natural river gravel with a limited grain size was used the collected data were analyzed using nondimensional groups developed in previous clear water studies it is shown that the imposed sediment transport does not require the introduction of new dimensionless parameters into existing scour depth and length prediction formula the effects of sediment feed are shown to be incorporated in the existing dimensionless parameters the new data set was used to recalibrate existing scour depth formula the influence of jet erosion on scour geometry is also discussed inspection of the data indicates a possible two stage behavior with the threshold between behaviors related to the ratio of the value of the morphological jump created at a scour hole and the flow specific energy at the bed sill

sediment transport through self adjusting bedrock walled waterfall plunge pools many waterfalls have deep plunge pools that are often partially or fully filled with sediment sediment fill may control plunge pool bedrock erosion rates partially determine habitat availability for aquatic organisms and affect sediment routing and debris flow initiation currently there exists no mechanistic model to describe sediment transport through waterfall plunge pools here we develop an analytical model to predict steady state plunge pool depth and sediment transport capacity by combining existing jet theory with sediment transport mechanics our model predicts plunge pool sediment transport capacity increases with increasing river discharge flow velocity and waterfall drop height and decreases with increasing plunge pool depth radius and grain size we tested the model using flume experiments under varying waterfall and plunge pool geometries flow hydraulics and sediment size the model and experiments show that through morphodynamic feedbacks plunge pools aggrade to reach shallower equilibrium pool depths in response to increases in imposed sediment supply our theory for steady state pool depth matches the experiments with an r 2 value of 0 8 with discrepancies likely due to model simplifications of the hydraulics and sediment transport analysis of 75 waterfalls suggests that the water depths in natural plunge pools are strongly influenced by upstream sediment supply and our model provides a mass conserving framework to predict sediment and water storage in waterfall plunge pools for sediment routing habitat assessment and bedrock erosion modeling

old carbon entering the south china sea from the carbonate rich pearl river basin coupled action of carbonate weathering and aquatic photosynthesis generally negative 14c values of riverine particulate organic carbon poc are interpreted as old carbon derived from the erosion of deep soils and sedimentary rocks here we present natural 14c and 13c data from the carbonate rich pearl river basin that discharges into the south china sea we found that the 14c values of poc and dic dissolved inorganic carbon transported by the carbonate rich river are all negative this however does not mean the poc is necessarily old but indicates control of carbonate weathering producing old dic with negative 14c values coupled with contemporary aquatic photosynthesis producing new autochthonous poc but with negative 14c values through the dead carbon effect of carbonate rocks which was further evidenced by particular seasonal change in 14c values of dic and poc both higher in the rainy season and lower in dry season spatial variation both getting higher downstream and negative correlation between 13c and age of poc this finding indicates that previous studies suggesting that riverine poc depleted in 14c is old may be problematic in carbonate dominated river basins the finding that river basins rich in carbonates can release old poc may have important implications for the interpretation of organic carbon age in rivers and coastal oceans affected by the runoff from this basin type it also indicates that it is necessary to examine the concentrations of both dic and autochthonous organic carbon in rivers to correctly assess the carbon sink produced by rock weathering

oceanic export of relict carbon by small mountainous rivers small mountainous rivers smr export globally significant quantities of particulate organic carbon poc to the oceans the composition of which may be distinct from poc delivered by major world rivers to better constrain the controls on the 14c signatures of poc suspended in smr we examined the temporal variability of 14c and 13c of poc suspended in the santa clara river a smr in california usa our data suggest mixing of bedrock and contemporary soil which can be applied to other smr in contrasting climate zones and with varying land cover the data also suggest that chemical denudation is incomplete but effective to the point that only the most recalcitrant moieties of the parent poc are exported we further propose sediment yield as a potentially useful proxy for the 14c of riverine poc a preliminary analysis of the existing data for a spectrum of rivers supports this hypothesis

atmospheric co2 sink silicate weathering or carbonate weathering it is widely accepted that chemical weathering of ca silicate rocks could potentially control long term climate change by providing feedback interaction with atmospheric co2 drawdown by means of precipitation of carbonate and that in contrast weathering of carbonate rocks has not an equivalent impact because all of the co2 consumed in the weathering process is returned to the atmosphere by the comparatively rapid precipitation of carbonates in the oceans here it is shown that the rapid kinetics of carbonate dissolution and the importance of small amounts of carbonate minerals in controlling the dissolved inorganic c dic of silicate watersheds coupled with aquatic photosynthetic uptake of the weatheringrelated dic and burial of some of the resulting organic c suggest that the atmospheric co2 sink from carbonate weathering may previously have been underestimated by a factor of about 3 amounting to 0 477 pg c a this indicates that the contribution of silicate weathering to the atmospheric co2 sink may be only 6 while the other 94 is by carbonate weathering therefore the atmospheric co2 sink by carbonate weathering might be significant in controlling both the short term and long term climate changes this questions the traditional point of view that only chemical weathering of ca silicate rocks potentially controls long term climate change

channel changes due to river regulation the case of the piave river italy this paper deals with the channel changes of the piave river in the eastern alps italy which have occurred during this century in response to human interventions in the fluvial system the flow regime and the sediment supply of the river have been considerably altered by hydroelectric dams flow diversions and gravel mining in addition river dynamics have been affected by the construction of streambank protection structures to document these changes a historical analysis was performed using maps and aerial photographs morphological features that were examined included planform configuration channel width braiding index and bed elevation the results indicate that as a consequence of decreases in the flows and sediment supply remarkable channel changes have occurred in the river during this century especially during recent decades the channel has undergone a general narrowing with a decrease in average width to 35 per cent of its initial value while the braiding index has decreased from about 3 to 1 5 in several reaches the planform pattern has changed from braided to wandering the observed trends of channel change suggest that the river has not yet reached a new equilibrium condition and it may therefore be predicted that reductions in width and braiding intensity are likely to continue in the immediate future copyright 1999 john wiley sons ltd

local scour upstream of a slit weir ordinary differential equation based model under steady and unsteady flow conditions abstracttime varying scouring upstream of a sediment release gate during a flood needs to be accurately predicted for reducing sedimentation around a water intake this paper presents an ordinary differential equation based model for computing time variation of scoured volume and maximum scour depth upstream of a slit weir for steady and unsteady flow the model is based on the sediment continuity equation and sediment entrainment volume from a scour hole there are some hypotheses in the model and these hypotheses were examined by carrying out 1 45 runs of scour inception tests 2 36 runs of numerical tests using computational fluid dynamics and 3 33 runs of physical scour tests measuring time variation of scoured topography the model was validated with the scour tests for steady and unsteady flow conducted in the present study in addition to those reported in different research the model was found to agree well with the data of time variation of the scoured volume and maximum scour depth allo

the geotechnical characteristics of an ice thrust mudstone wabamun lake area alberta this first detailed report of the geotechnical characteristics of ice thrust soft rock examines upper cretaceous once heavily overconsolidated mudstones in the highvale coal mine alberta the fissured and brecciated sample from an ice thrust shear zone in the mine behaves as a lightly overconsolidated sediment in laboratory tests and shows a non brittle mode of shear deformation with a maximum shear strength close to residual this behaviour is due to weathering and glaciotectonic deformation which have jointed sheared and remoulded the mudstone thus eliminating the fabric formed by overconsolidation in the ice thrust mudstone platy clay minerals dominate and have been grouped into aggregations or shear remoulded matrices the strength of the brecciated portion of the mudstone ranges from peak to residual the strength along principal displacement shears is at or close to residual as back analysis of a slope failure shows key words ice thrust shear zone glaciotectonic deformation consolidation

time variation of scour at abutments a semiempirical model is presented to compute the time variation of scour depth in an evolving scour hole at short abutments abutment length flow depth 1 namely the vertical wall 45 wing wall and semicircular in uniform and nonuniform sediments under a clear water scour condition the methodology developed for computing the time variation of scour depth is based on the concept of the conservation of the mass of sediment considering the primary vortex system as the main agent of scouring and assuming a layer by layer scouring process for an equilibrium scour hole the characteristic parameters affecting the nondimensional equilibrium scour depth scour depth abutment length identified based on the physical reasoning and dimensional analysis are excess abutment froude number flow depth abutment length ratio and abutment length sediment diameter ratio experiments were conducted for time variation and equi librium scour depths at different sizes of vertical walls 45 wing walls and semicircular abutments in uniform and nonuniform sediments under limiting clear water scour conditions approaching flow velocity nearly equal to the critical velocity for bed sediments the present model corresponds closely with the data of time variation of scour depth in uniform and nonuniform sediments obtained from the present experiments and reported by different investigators

mesofabric microfabric and submicrofabric of ice thrust bedrock highvale mine wabamun lake area alberta the fabric of the ice thrust argillaceous bedrock from a shear zone was studied in hand specimens under a polarizing microscope and a scanning electron microscope the fabric included principal di

coal quality coal rank variation and its relation to reconstructed overburden upper cretaceous and tertiary plains coals alberta canada near surface coals in the alberta plains occur in upper cretaceous and tertiary sediments the former represented by the belly river group horseshoe canyon formation and wapiti formation and the latter by the scollard member of the paskapoo formation statistical techniques were used to document both the distribution of and the interrelationships among the components of proximate and ultimate analysis and calorific value determinations the coals discussed range in rank from subbituminous c to high volatile bituminous c these coals are variable in ash content and low in sulfur content the relationships among calorific value dry basis in kj kg and ash dry basis in and calorific value moist mineral matter free basis in kj kg and equilibrium moisture meq in were determined to be cvd 29 677 315 17 ashd and cvmmmf 31 816 442 05 meq respectively the maximum depth of coal seam burial dob in m was reconstructed on the basis of previously published graphs relating the equilibrium moisture loss to depth of coal seam burial using the relationship log10meq 1 865 0 000416 dob a least squares regression analysis of calorific value mmmf basis in k kg on the calculated depth of burial dob in m yielded the equation cvmmmf 14 748 6 25 dob indicating a coalification gradient determined on the reconstructed overburden of 6 25 kj kg m 0 82 btu lb ft of depth or overburden near surface coals in the alberta plains increase in rank toward the west southwest toward the foothills and mountains region because of progressively greater amounts of overburden that existed in that direction during the tertiary erosion has since removed between 900 and 1 900 m 3 000 and 6 200 ft of sediment with the greatest amount of removal occurring in a west southwest direction

scour below a high vertical drop experimental results on scour below a high vertical drop drop height critical depth 1 in uniform sands and gravels are presented the experimental results are used to describe the effects of important parameters identified from the dimensional analysis on equilibrium scour depth the important observations are that the equilibrium scour depth increases with increase in densimetric froude number whereas the scour depth decreases with increase in sediment size and tailwater depth the time scale of scour depth that follows an exponential law is determined the nondimensional time scale decreases with increase in densimetric froude number

scouring at bed sills as a response to flash floods the temporal development of clear water local scour depth at bed sills in uniform gravel beds is considered experiments are presented on the development of scour holes under unsteady hydraulic conditions with the triangular shaped hydrographs tested being of different durations and different rates of flow variation based on the experimental results and a theoretical framework a method is given for the definition and prediction of the scouring process under unsteady flows in terms of a dimensionless temporal parameter a flash flood is here defined as an event for which the scour doesn t attain its potential magnitude i e the equilibrium value for the peak hydrograph flow rate this flood nature is dependent on both the characteristics of the flood event itself and the characteristics of the stream a quantitative measure of what constitutes a flash flood is given in terms of the identified temporal parameter results show that the ratio between the final scour depth and the potential scour depth

modelling time varying scouring at bed sills in this paper a modelling approach is presented to predict local scour under time varying flow conditions the approach is validated using experimental data of unsteady scour at bed sills the mode

sources and compositional distribution of organic carbon in surface sediments from the lower pearl river to the coastal south china sea the pearl river plays an important role in transporting terrestrial organic carbon oc to the south china sea scs however the sources and compositional distribution of oc in the system are poorly understood this study focused on delineating the sources and determining the fate of surface sedimentary oc from the feilaixia hydropower station to the coastal scs elemental stable carbon nitrogen isotope 13c and 15n and lignin phenol analyses have been conducted the total oc toc from the upstream sites were generally derived from vascular plants higher c n and and depleted 13c and soils additional input was attributed to riverine primary production lower c n and enriched 13c which was enhanced near the dam created reservoir the c n and 13c values were not significantly different among sites in the midstream the estuary coastal sites witnessed hydrodynamically sorted riverine oc which was diluted by marine primary production lower c n and more enriched 13c the lignin concentration was the highest in the upstream sites remained relatively unchanged in the midstream sites and decreased significantly along the estuary coastal sites which was corroborated by variation in toc a comprehensive five end member monte carlo simulation suggested that previous studies had underestimated the c4 plant input by 14 11 and overestimated the riverbank soil input by 21 17 thus our study provided valuable information for more accurate source and mass balance studies of terrestrial oc transported to the scs which helped to further understand the carbon cycling in the large river ocean continuum

channel morphology gradient profiles and bed stresses during flood in a step pool channel abstract the stability of a step pool channel is investigated on the basis of measurements during a median annual flood the study reaches range in gradient from 5 to 10 and the flow was 3 m3 s 1 in an 8 m wide channel the estimated shear stress based on the channel gradient was 102 pa which implies that the channel ought to move half meter class boulders calculations of the shear stress using flow resistance equations yield values of about 30 pa these figures imply that the largest boulders in the channel could be moved in fact the channel is stable the effective stress remains well below the threshold to move the large structure forming boulders the steps are stable structures that result from interlocking of the larger stones they are semi randomly located depending on the location of keystones that are deposited in the channel by debris flows or fall out of the banks the high variation in step pool wavelength step height residual pool depth and pool length is indicative of the random nature of step location and structure along a reach there is no convincing evidence that special conditions govern their formation

erosion by planar turbulent wall jets new scaling laws are presented for the spatial variation of the mean velocity and lateral extent of a two dimensional turbulent wall jet flowing over a fixed rough boundary these scalings are analogous to those derived by wygnanski et al 1992 for the flow of a wall jet over a smooth boundary they reveal that the characteristics of the jet depend weakly upon the roughness length associated with the boundary as confirmed by experimental studies rajaratnam 1967 these laws are used in the development of an analytical framework to model the progressive erosion of an initially flat bed of grains by a turbulent jet the grains are eroded if the shear stress exerted on the grains at the surface of the bed exceeds a critical value which is a function of the physical characteristics of the grains after the wall jet has been flowing for a sufficiently long period the boundary attains a steady state in which the mobilizing forces associated with the jet are insufficient to further erode the boundary the steady state profile is calculated separately by applying critical conditions along the bed surface for the incipient motion of particles these conditions invoke a relationship between the mobilizing force exerted by the jet the weight of the particles and the local gradient of the bed use of the new scaling laws for the downstream variation of the boundary shear stress then permits the calculation of the shape of the steady state scour pit the predicted profiles are in good agreement with the experimental studies on the erosive action of submerged water and air jets on beds of sand and polystyrene particles rajaratnam 1981 the shape of the eroded boundary at intermediate times before the steady state is attained is elucidated by the application of a sediment volume conservation equation this relationship balances the rate of change of the bed elevation with the divergence of the flux of particles in motion the flux of particles in motion is given by a semi empirical function of the amount by which the boundary shear stress exceeds that required for incipient motion hence the conservation equation may be integrated to reveal the transient profiles of the eroded bed there is good agreement between these calculated profiles and experimental observations rajaratnam 1981

response of dissolved inorganic carbon dic and δ13cdic to changes in climate and land cover in sw china karst catchments abstract monthly hydrochemical data and 13c of dissolved inorganic carbon dic in karst water samples from september 2007 to october 2012 were obtained to reveal the controlling mechanisms on dic geochemistry and 13cdic under different conditions of climate and land cover in three karst catchments banzhai dengzhanhe and chenqi in guizhou province sw china dic of karst water at the banzhai site comes mainly from carbonate dissolution under open system conditions with soil co2 produced by root respiration and organic carbon decomposition with lowest 13c values under its dense virgin forest coverage weaker carbonate bedrock dissolution due to sparse and thin soil cover results in lower 13cdic pco2 dic and ec and lower cation and anion concentrations at the chenqi site larger soil co2 input from a thick layer of soil results in high pco2 and dic and low ph sic and 13cdic in the karst water at the dengzhanhe site a lesser soil co2 input due to stronger karst rock desertification and strong gypsum dissolution contribute to higher 13cdic high ec and high cation and anion concentrations soil co2 inputs controlled by biological activity and available soil moisture carbonate bedrock dissolution dilution and degassing effects vary seasonally following rainfall and temperature changes consequently there are seasonal cycles in hydrochemistry and 13cdic of the karst water with high pco2 and low ph ec sic and 13cdic values in the warm and rainy seasons and vice versa during the cold and dry seasons a strongly positive shift 3 in 13cdic occurred in the drought year 2011 indicating that 13cdic in groundwater systems can be an effective indicator of environmental and or climate changes

sources of sedimentary organic matter in the mississippi river and adjacent gulf of mexico as revealed by lipid biomarker and δ13ctoc analyses abstract changes in the organic matter om composition c n 13 c toc and lipid biomarker compounds of surface sediments 0 1 cm were examined along the dispersal pathway from mississippi river and marsh estuarine end members to the adjacent shelf and canyon regions of the gulf of mexico organic carbon content decreased fourfold from the marsh to the offshore sites with corresponding changes in organic matter sources biomarkers representing allochthonous higher plant and autochthonous algal plankton bacteria sources demonstrated regional differences in the sources of sediment organic matter som a two end member mixing model using 13 c toc indicated that c 3 vascular plant sources comprised 80 and 50 of the toc at the river and marsh sites respectively however sources of som differed in these regions with contributions of soil organic matter terrigenous plant sources dominant in the river 13 c toc 25 while marsh plants likely contributed to the enriched signatures found in the marsh sediments 13 c toc 18 allochthonous om contributions calculated from fatty acid and sterol biomarkers in the river and marsh regions 39 48 and 50 72 respectively differed from those determined using 13 c toc this was likely due to overlapping 13 c toc values for vascular plants and freshwater microalgae and the higher lipid content of the autochthonous sources although biomarkers representing terrigenous sources decreased with distance offshore they comprised approximately 17 34 of the fatty acid and sterols at even the most distal slope and canyon sites suggesting that these deeper regions could be an important sink for terrigenous carbon in contrast the shelf sites were enriched in algal material 60 78 autochthonous oc with biomarkers for diatoms dominating suggesting that terrigenous carbon is either diluted in or bypasses this region results from this study suggest that processes including hydrodynamic sorting diagenesis and variations in river flow should be considered in future studies investigating the fate of terrigenous om in coastal and shelf regions

from peat bog to lignite seam a new method to calculate the consolidation coefficient of lignite seams wielkopolska region in central poland only one quantitative method is described in the literature to estimate the consolidation coefficient of lignite seams more studies concentrate on the compaction of plant tissues which explains why the obtained results are overestimated moreover most studies do commonly not determine the consolidation of the whole peat bog but usually those of some of its elements only we propose a new approach which conceptually is fairly close to the hager et al fortschr geol rheinld westf 29 319 352 1981 method our method has been tested on an example of the first middle polish lignite seam and the second lusatian lignite seam from some wielkopolska lignite deposits in central poland the consolidation coefficients cc range between 2 34 and 2 56 for the second lusatian lignite seam and between 1 80 and 2 14 for the first middle polish lignite seam

geothermal gradients hydrodynamics and hydrocarbon occurrences alberta canada using coal rank data and the demonstrated genetic link between the present hydrodynamic regime and geothermal gradient pattern it is possible to reconstruct the geothermal history of alberta over the past 60 m y palinspastic adjustment for tectonic compression caused by the major laramide thrusting shows that the predeformation isoreflectance lines increased logarithmically with depth in the late paleocene the geothermal gradient was about 23 c km 1 25 f 100 ft in the eastern alberta plains compared to about 30 c km 1 65 f 100 ft in the western alberta plains a regional trend opposite to the post laramide trends reconstruction of the early eocene surface indicates western uplands with geothermal gradients as low as 21 c km 1 15 f 00 ft and eastern lowlands with geothermal gradients of 27 c km 1 5 f 100 ft compared to the present situation this represents an enhanced topographic surface and a subdued geothermal gradient pattern the genetic relations of topography water table elevation hydrodynamic regime and geothermal gradient pattern in both the early eocene and the present conform to a model developed for any compacted sedimentary basin with subaerial relief in this model on a regional scale high topographic areas have high water table elevations with correspondingly high potentiometric surfaces these areas control the regional recharge of cold meteoric water and hence have low geothermal gradients areas of medium elevation exhibit regional lateral flow and intermediate geothermal gradients regional topographic lows correspond with low potentiometric surfaces and the regional discharge of warm formation waters from deep in the basin results in high geothermal gradients local topographic featur s cause perturbations in this picture study of both the regional pattern and fine detail of the early eocene and present topographic surfaces and geothermal gradient patterns shows the validity of the model the result of the second laramide orogenic pulse was therefore to reverse the geothermal gradient pattern resulting mainly from compaction flow and to impose a topographically controlled hydrodynamic regime with flow in the same direction but with a 9 c km 0 5 f 100 ft decreased geothermal gradient in western alberta and a 4 c km 0 2 f 100 ft increased geothermal gradient in eastern alberta as erosion proceeded during the tertiary the entire alberta basin warmed up until the present temperature regime was attained study of some major hydrocarbon occurrences shows a genetic link between the hydrocarbon occurrence and the present fluid regime which itself is controlled by the present topography for at least the significant upper cretaceous shallow gas reserves in southeastern alberta however their position may already have been determined as early as the beginning of the eocene by the topographic surface at that time therefore the extent to which the present topographic surface is responsible for hydrocarbon accumulation through gravity induced cross formational flow remains unknown because this process was operative as long ago as the early eocene what does not ap ear to be in doubt is the fact that gravity induced cross formational flow does control the hydrodynamic regime which in turn influences the geothermal gradient pattern and the accumulation of hydrocarbons

disturbance caused by bed sills on the slopes of steep streams live bed tests on steep bed slopes are run in a laboratory flume to investigate the slope of equilibrium the tests simulate a general degradation until a new equilibrium is reached subsequently different bed sill settings are tested as a countermeasure against degradation evidence is presented that in some cases the bed slope with sills is milder than the one without sills under the same flow and sediment rates this fact implies that the efficiency of the bed sill system to stop degradation decreases as the sills are placed closer together tests are on the verge of sheet flow and friction factors are heavily dependent on sediment transport reaches in uniform and gradually varied flow behave very differently bed profiles are not straight and grain size is linked to this fact other detailed information on testing equipment experimental program time development and local scour in a total number of 111 tests is given

karst biogeochemistry in china past present and future the dissolution and deposition processes of carbonate rock called co2 water carbonate rock interaction are controlled by complex interactions among the biosphere pedosphere atmosphere and lithosphere the interactions between biogenic activity and the co2 water carbonate rock system dissolution and precipitation of carbonate rocks element cycles and so forth had been named karst biogeochemistry in order to reveal their internal control mechanism over space and time chinese researchers undertook an in depth exploration of their interrelationships the main results of karst biogeochemistry in china can be summarized as follows i biogenic activity plays an important role in regulating dissolution and precipitation of carbonate rocks ii biogenic metabolic effects are involved in the positive or negative modulation of 13c 15n and the cycling of other elements iii co2 exchange during carbonate rock dissolution and precipitation which is mainly due to photosynthesis results in the accumulation of organic matter and iv primary karst biogeochemistry models have been established to evaluate carbon and nitrogen cycling in addition to these findings future studies should increasingly focus on the following topics i the apparent stability and transformation of dissolved organic carbon caused by microbial activities need to be clarified ii the temporal spatial scales of microbial biomineralization and the accompanying variances of karst biogeochemical cycles should be investigated to comprehensively understand the transformations and transport of substrates from biological activity in the co2 water carbonate rock system iii regional global scale models on karst biogeochemical cycles should be developed for the study of large small scale spatial and temporal variance on karst biogeochemical cycles iv new advanced techniques and methods are required and should be applied for the karst studies involving mathematics hydrochemistry isotope chemistry geology biology and so forth

analysis of small scale gravel bed topography during armoring 1 in evaluating the resistance of sediment particles to entrainment by the action of the flow in a river the grain geometry is usually characterized using representative sizes this approach has been dictated initially by lack of physical insight but more recently by the lack of analytical tools able to describe the 3 d nature of surface grain organization on water worked sediment beds laboratory experiments are presented where mixed grain size beds were mobilized under a range of hydraulic and sediment input conditions detailed bed topography was measured at various stages statistical tools have been adopted which describe the degree of surface organization on water worked sediment bed surfaces the degree of particle organization and the bed stability can be evaluated in relative terms using the properties of the probability density distribution of the bed surface elevations and in absolute terms using a properly defined 2 d structure function the methods described can be applied directly to natural water worked surfaces given the availability of appropriate bed surface elevation data sets

local scour due to submerged horizontal jet the phenomena of local scour and sediment transport due to a horizontal jet issuing from a sluice and flowing over a rigid apron then on to an erodible bed have been investigated based on experimental data the scour characteristics have been correlated through the development of empirical expressions for the time to reach equilibrium stage the locations of maximum scour depth and peak of dune and the variation of maximum scour depth with time similarity criteria for the predication of development of the scour hole and sediment transport have also been developed and apart from the flow parameters and sediment properties the jet diffusion characteristics play an important role in these processes the empirical relationships developed in this study highlight the necessity of an individual assessment when developing the similarity criteria for a particular flow situation

evolution of scouring process downstream of grade control structures under steady and unsteady flows for many incised channels one of the most common strategies is to install some hard structures such as grade control structures gcss in the riverbed to resist further incision in this study a series of experiments including both steady and unsteady flow conditions were conducted to investigate the scouring process downstream of a gcs three distinct phases including the initial developing and equilibrium phases during the evolution of scour holes were identified in addition a semi empirical method was proposed to predict the equilibrium scour hole profile for the scour countermeasure design in general the comparisons between the experimental and simulated results are reasonably consistent as the studies on temporal variation of the scour depth at gcss caused by floods are limited the effect of flood hydrograph shapes on the scour downstream of gcss without upstream sediment supply was also investigated experimentally in this study based on the dimensional analysis and the concept of superposition a methodology is proposed to simulate the time evolution of the maximum scour depth downstream of a gcs for steady flows moreover the proposed scheme predicts reasonably well the temporal variations of the maximum scour depth for unsteady flows with both single and multiple peak copyright 2012 john wiley sons ltd

time scale for local scour at bridge piers the temporal development of clear water local scour depth at cylindrical bridge piers in uniform sand beds is considered new data are presented and used to quantify the influence of flow duration on the depth of local scour an equilibrium time scale t is defined the data show that both t and the equilibrium scour depth dse are subject to similar influences of flow and sediment parameters as might be expected because they are inherently interdependent a method is given for determination of the time for development of dse for a given pier sediment and approach flow velocity and the concomitant estimation of the scour depth at any stage during development of the equilibrium scour hole the results show that the scour depth after 10 of the time to equilibrium is between about 50 and 80 of the equilibrium scour depth depending on the approach flow velocity of local scour d se is rapidly attained in live bed conditions but rather more slowly in clear water conditions fig 1 clear water scour occurs for mean flow velocities up to the threshold velocity for bed sediment entrainment i e v vc while live bed scour occurs for v vc the maximum equilibrium scour depth dse max occurs at v vc in armored cobble or cohesive sediment bed streams multiple flood events may be required before the maximum clear water scour is reached this may take many years the equilibrium scour depth in live bed con ditions fluctuates due to the effects of bed form migration the dashed lines in fig 1 represent the temporal average scour depth under live bed conditions the diagram also shows the time taken te for the equilibrium scour depth to develop the equilibrium time te is the focus of this paper it increases rapidly with flow velocity under clear water conditions but then decreases rapidly for live bed scour existing equations for depth of local scour at bridge piers give the equilibrium depth and are therefore conservative re garding temporal effects for the live bed conditions that typ ically pertain in floods equilibrium scour depths are appro priate however where clear water scour conditions exist the equilibrium depth of scour may be overly conservative peak flood flows may last only a number of hours or a few days in the field and short floods have insufficient time to generate equilibrium depths for example bridge piers situated on the floodplain may be wet for periods of less than one day during a flood typically clear water conditions pertain at such sites the actual scour may be only a small fraction of the equilib rium scour depth which could take weeks to fully develop johnson and mccuen 1991 developed an analytical model to simulate the temporal process of local scour at piers the model was applied to a hypothetical bridge pier using a gen erated sequence of flood flows over a 75 year period the in dividual storms being of 24 h duration at the end of the 75 year period the scour depth was still increasing

new views on old carbon in the amazon river insight from the source of organic carbon eroded from the peruvian andes 1 mountain rivers play a key role in the delivery of particulate organic carbon poc to large river systems and the ocean due to the extent of its drainage area and runoff the amazon river is one of earth s most important biogeochemical systems however the source of poc eroded from the humid region of the eastern andes and the input of fossil poc from sedimentary rocks pocfossil remains poorly constrained here we collected suspended sediments from the kosnipata river during flood events to better characterize andean poc measuring the nitrogen to organic carbon ratio n c stable carbon isotopes 13corg and radiocarbon 14corg 14corg values ranged from 711 to 15 and significant linear trends between 14corg n c and 13corg suggested that this reflects the mixing of pocfossil with very young organic matter 14corg 50 from the terrestrial biosphere pocnon fossil using n c and 14corg in an end member mixing analysis we quantify the fraction of pocfossil to within 0 1 and find that it contributes a constant proportion of the suspended sediment mass 0 37 0 03 and up to 80 of total poc in contrast the relative contribution of pocnon fossil was variable being most important during the rising limb and peak discharges of flood events the new data shed light on published measurements of old poc low 14corg in andean fed tributaries of the amazon river with their 14corg and 13corg values consistent with variable addition of pocfossil the findings suggest a greater persistence of andean poc in the lowland amazon than previously recognized

carbon isotope geochemistry of the santa clara river the santa clara river is a prototypical small mountainous river with a headwater height greater than 1000 m and a basin area smaller than 10 000 m 2 although individual small mountainous rivers export trivial amounts of sediment and carbon to the ocean as a group these rivers may export a major fraction as much as 50 of the total global river sediment flux milliman and syvitski 1992 making their geochemistry relevant the study of the ocean s carbon cycle in addition many small rivers export sediment in a few high flux events causing massive sporadic discharge of carbon onto coastal shelves discharge conditions very different from those of large rivers this class of rivers is an end member of the river ocean carbon exchange system opposite the earth s largest river the amazon the carbon mass and isotopic properties of the santa clara river are significantly different from previously studied large rivers during the 1997 1998 winter all santa clara carbon pools were old with flux weighted average l4c values of 428 76 for particulate organic carbon 73 31 for dissolved organic carbon and 644 58 for black carbon the age of exported carbon is primarily due to the deep erosion of old soils and not to inclusion of fossil fuel carbon additionally the 13c signatures of exported carbon pools were high relative to terrestrial carbon bearing a signature quite similar to marine carbon average particulate organic carbon poc 13c 22 2 0 8 the santa clara s estuary is small and drains onto the narrow eastern pacific coastal margin exporting this old soil organic matter directly into the ocean if the santa clara export patterns are representative of this class of rivers they may be a significant source of refractory terrestrial carbon to the ocean

diagenesis of the devonian southesk cairn carbonate complex alberta canada marine cementation burial dolomitization thermochemical sulfate reduction anhydritization and squeegee fluid flow abstract one of the largest geological features in the deep part of the alberta basin in western canada is the middle to upper devonian southesk cairn carbonate complex sccc the sccc is located at depths of about 5000 m adjacent to the disturbed belt of the rocky mountains rising to depths of 3000 m in a northeastward direction over a distance of 150 km the sccc produces oil and gas with up to about 30 h2s from several stratigraphic levels the diagenesis of the sccc was investigated by means of petrography and geochemistry stable isotope compositions were determined for fibrous calcite cements matrix dolomite saddle dolomite and sparry calcite fibrous calcites have stable isotope values of 18o 7 5 to 4 5 pdb and 13c 2 0 1 0 pdb matrix dolomite samples have stable isotope values of 18o 8 1 to 4 9 pdb and 13c 0 to 1 0 pdb saddle dolomite samples range from 18o 9 8 to 7 1 pdb and 13c 1 0 to 0 pdb sparry calcite samples have 18o 13 7 to 7 2 pdb and 13c 24 0 to 0 pdb the sr isotope values of all analyzed samples span a broad range from 0 7080 to 0 7320 showing considerable scatter but also one distinctive pattern i e values higher than 0 7220 occur only at depths in excess of about 4000 m whereas lower values scatter throughout the entire depth range furthermore the sr isotope values of sparry calcites decrease northeastward similarly the fluid inclusion homogenization temperatures of these calcites display a general decrease updip whereas the salinities show no general spatial trends the uncorrected homogenization temperatures range from about 85 to 180 c and the nacl equivalent salinities range from about 17 to 24 weight the d values of brines obtained from seven wells range from 79 to 20 smow and their 18o values range from 1 5 to 8 7 smow the sulfur isotope values of the dissolved sulfate ranges from 34s 10 1 to 24 5 cdt the sr isotope values of the brine samples range from 0 7109 to 0 7255 elemental sulfur isotope values cluster tightly around 34s 18 0 to 18 4 cdt the values of secondary anhydrites range from 34s 18 4 to 26 7 cdt values for solid bitumen vary from 34s 19 5 to 20 2 cdt integration of all data reveals a complex diagenetic evolution from the middle devonian to the recent the paragenetic sequence consists of 24 distinct diagenetic phases which have been grouped into 5 diagenetic stages stage i density driven convection in near surface settings likely superimposed on and or aided by tidal pumping facilitating marine cementation stage ii cellular convection facilitating pervasive matrix dolomitization aided by compaction stage iii hydrocarbon migration stage iv thermochemical sulfate reduction forming sour gas and regional squeegee flow forming sparry calcite cements and localized flow through faults stage v fluid flow driven by erosional rebound in the overlying mesozoic strata and remnant squeegee flow this study yielded several important results 1 the prolific repertoire of diagenetic textures found in the southesk cairn carbonate complex serves as a means of comparison for petroliferous carbonate complexes elsewhere especially in sour gas provinces close to orogenic fronts 2 the diagenetic evolution contains long periods of relative tranquility that were punctuated by several episodes of intense diagenetic activity 3 both thermochemical sulfate reduction and squeegee type fluid flow are recorded in late diagenetic sparry calcite cements 4 the effect of the various burial diagenetic episodes on the hydrocarbon reservoir properties throughout the entire reef complex was highly variable specifically matrix dolomitization thermochemical sulfate reduction and the emplacement of secondary and tertiary anhydrites affected the hydrocarbon reservoir properties throughout the entire reef complex on the other hand squeegee fluid flow was insignificant in terms of affecting the reservoir properties

loss of organic matter from riverine particles in deltas abstract in order to examine the transport and burial of terrigenous organic matter along the coastal zones of large river systems we assessed organic matter dynamics in coupled river delta systems using mineral surface area as a conservative tracer for discharged riverine particulate organic matter pom most pom in the rivers studied n 6 is tightly associated with suspended mineral material e g it is sorbed to mineral surfaces average organic loadings in the amazon river 0 67 0 14 mg c m 2 the river for which we have the largest dataset are approximately twice that of sedimentary minerals from the amazon delta 0 35 mg c m 2 stable carbon isotope analysis indicate that approximately two thirds of the total carbon on the deltaic particles is terrestrial the combined surface normalized isotope distinguished estimate is that 70 of the amazon fluvial pom is not buried in the delta consistent with other independent evidence aller et al 1996 losses of terrestrial pom have also been quantified for the river delta systems of columbia in the usa fly in new guinea and huange he in china if the losses of riverine pom observed in these river delta systems are representative of rivers worldwide then the surface constrained analyses point toward a global loss of fluvial pom in delta regions of 0 1 x 1015 g c y 1

local scouring and morphological adjustments in steep channels with check dam sequences this paper describes bed profile and grain size distribution adjustments in a mountain river maso di spinelle river italian alps stabilized by a sequence of boulder check dams the control works were originally designed to simulate the geometry of natural step pool channels where tumbling flow is the dominant hydraulic regime local scouring downstream of 29 drop structures is analysed through the use of nondimensional parameters where maximum scour depth and scour length are normalised to the drop height prior laboratory data reveal a pattern similar to field scours where complex interactions occur between drop height critical flow depth and step spacing the linkage between scour length and depth is also discussed there seems to be a maximum step height for impinging jets that is approximately twice the drop height this maximum may explain the upper limit of the steepness factor found in high gradient step pool streams if such a maximum upper limit is confirmed by further studies this may aid designs of foundation heights for transverse control works in steep channels

morphological effects of local scouring in step pool streams step pool morphology characterizes many high gradient streams in a variety of natural settings but formative processes and evolutionary dynamics are still poorly understood in this paper natural step pool geometry is compared with steep alluvial channels where grade control structures such as check dams and bed sills make the stream profile resemble a natural stepped stream along these channels local scouring due to falling jets forms plunge pools under each structure analogous to natural steps determining the formation of pools in order to test the hypothesis that natural pools are analogous to pools formed below grade control works with respect to their dimensions shape and formative dynamics 37 natural pools and 73 artificial pools were surveyed in 10 mountain streams of the eastern italian alps pools below grade control works featured a transitional zone between the scour hole and the downstream sloping bed marked by a depositional berm when geometric parameters such as maximum pool depth length and step berm distances are normalized to the jet virtual energy no statistically significant differences were detected between natural and artificial systems these results lend support to an upstream forced cascade model for step pool formation where the energy of falling jets controls the geometry of the pools and is therefore regarded as the most important scaling independent variable copyright 2005 john wiley sons ltd