origin of minerals and elements in the late permian coals tonsteins and host rocks of the xinde mine xuanwei eastern yunnan china abstract this paper reports the mineralogical and geochemical compositions of the late permian c2 and c3 coals both medium volatile bituminous coal from the xinde mine near xuanwei in eastern yunnan which is located close to the area with the highest female lung cancer mortality in china the two coals are characterized by high ash yields and low sulfur contents three factors including sediment source region multi stage volcanic ash generation and multi stage hydrothermal fluid injections were responsible for variations in the geochemical and mineralogical compositions of the xinde coals trace elements including v sc co ni cu zn se zr nb hf and ta are enriched in the coals and were mainly derived from the sediment source kangdian upland region major minerals in the samples of coal roof floor and non coal sediment partings include quartz kaolinite and chamosite as well as interstratified illite smectite and anatase chamosite in the coal was derived from reactions between kaolinite and fe mg rich hydrothermal fluids however chamosite in the roof strata was directly precipitated from fe mg rich hydrothermal fluids or was derived from the alteration of precursor minerals e g biotite by hydrothermal fluids quartz in some samples is very high especially in the roof strata of the c2 and c3 coal such high quartz along with minor minerals including pyrite chalcopyrite sphalerite calcite celestite vanadinite barite clausthalite and silicorhabdophane were derived from multi stage hydrothermal fluids the floors of both the c2 and c3 coal seams are fully argillized fine grained tuffaceous claystone and the immediate roof of the c2 coal is argillized coarse grained tuff the original materials of the floors and roofs of these coal seams were high ti alkali basaltic volcanic ashes as indicated by high tio 2 nb and siderophile elements and the distribution patterns of rare earth elements two intra seam tonstein layers in the c3 coal were identified based on their lateral persistence mineralogical mode of occurrence and composition as well as their elemental composition the tonsteins are dominated by kaolinite with minor quartz and possibly mixed layer illite smectite both tonsteins were derived from dacitic magma the ratios of nb ta zr hf and u th are much lower in tonsteins than in the adjacent coal benches which is attributed to the hydrothermal leaching

glacially conditioned specific stream powers in low relief river catchments of the southern laurentian great lakes abstract fluvial systems of the southern laurentian great lakes region are carved into a complex glacial landscape shaped by continental ice and meltwater of the late pleistocene these glacially conditioned river catchments are typically small with drainage areas 4 km 2 a 10 m digital elevation model dem is used to map the spatial distribution of stream gradient for 22 major river catchments of peninsular southern ontario which drain to base levels in the lower great lakes huron st clair erie and ontario raw data from the dem show stream gradients that exhibit multiscale variance from real and from artifact sources based on a vertical slice and multiple pass moving window averaging approach slope data are generalised to the river reach scale 1 2 km as a representative spatial scale for fluvial processes operating over holocene timescales models of specific stream power are then compared with glacial landform and surface geology mapping inherited glacial signatures in river slope appear as deviations in a stream length gradient index sl k index where river reaches are frequently oversteepened or understeepened based on a slope area analysis and complementary to theories of channel pattern discrimination constant stream power curves with power law exponent of 0 4 provide a first order approach to stratify river reaches in terms of glacial conditioning and expected planform morphologies however multiple channel planform types are rare and localised in southern ontario indicating that oversteepened reaches with high stream powers may often be moderated by 1 sediment calibre with cobble beds from inherited glacial sediments and or 2 relative bank strength with limited channel widening particularly in gravel and sand bed channels further discrimination of glacially conditioned fluvial process domains will ultimately require consideration of alluvial floodplain characteristics in addition to general observations of river morphology and channel pattern

mineralogical composition of late permian coal seams in the songzao coalfield southwestern china abstract coals from three seam sections in the songzao coalfield sw china are mainly high ash high sulphur semianthracites minerals within the songzao coals are mainly kaolinite pyrite or marcasite in some cases and quartz with various proportions of non kaolinite clay minerals carbonates feldspars and anatase the illite and mixed layer illite smectite i s are na rich in some of the datong coal samples the i s in the lower coals of the datong section is most likely an alteration product of dispersed volcanic ash due to the availability of necessary ions e g k na and mg in the marine influenced coal swamp organically bound na which was expelled from the organic matter with coal rank advance especially with anthracitization may have supplied additional na for the formation of na rich illite authigenic i s also occurs in a tonghua coal ply that is overlain by a mafic bentonite and underlain by an alkali tonstein potassium na and mg for the formation of such i s were probably derived from the leaching of the adjacent alkali tonstein and mafic bentonite although the marine water was also a possible supplier of the alkali elements authigenic i s is rare in coal plies that occur further away from the altered volcanic layer leaching of the volcanic claystones in the tonghua coal seam probably led to the formation of relatively abundant anatase and rhabdophane in the underlying coal ply fracture filling ree minerals probably ree hydroxides or oxyhydroxides also occurring in that coal ply crystallized from ascending ree rich hydrothermal fluids probably associated with contemporaneous volcanic activity

distribution of rare earth elements in eastern kentucky coals indicators of multiple modes of enrichment abstract four eastern kentucky pennsylvanian coals from oldest to youngest the manchester pond creek fire clay and hazard coals were examined for their total rare earth element rey concentration and the possible mechanisms for enrichment of the rare earths based on previous studies four possible modes are considered terrigenous tuffaceous infiltrational and hydrothermal with the dean coal a correlative of the fire clay coal considered to be a typical example of the tuffaceous mode the fire clay owes much of its high rey content to the presence of a volcanic ash fall tonstein with rey bearing zircon and phosphates in the coal in numerous locations some of the original rey elements may have components of the detrital minerals deposited in the peat leaching of rey from the tonstein into the surrounding coal and the hydrothermal overprint of mineralizing fluids associated with the northwestwardly movement of the pine mountain thrust sheet contributed to the total rey signature in the fire clay coal not all coals are going to have the complex history of the fire clay coal but it should be considered that the total history of rey enrichment by multiple mechanisms is what gives us both the total rey concentration and the relative distribution of the individual lanthanide elements

mineralogy of the pennsylvanian coal seam in the datanhao mine daqingshan coalfield inner mongolia china genetic implications for mineral matter in coal deposited in an intermontane basin abstract this paper deals with the mineral matter in the coal and associated strata from the datanhao mine daqingshan coalfield which is closely located to the previously reported adaohai and hailiushu mines of the same coalfield the coal from the datanhao mine is mainly high ash and low sulfur bituminous the mineral assemblage in the coal is dominated by quartz kaolinite with varying proportions of carbonates calcite ankerite and siderite small proportions of muscovite illite pyrite and anatase the associated non coal claystone samples have similar mineral assemblage except that most non coal samples contains less quartz than the adjacent coal plies although deposited in the same intermontane basin of the orogenic belt the yinshan upland the datanhao coal seam shows different mineralogical characteristics from those of the nearby adaohai and hailiushu mines this may reflect the different sediment source regions during the peat accumulation stage the sediment source for the datanhao coal was probably the ordovician quartz rich sandstone or the sinan quartzite in the surrounding sub uplifts high proportions of quartz in the datanhao coal suggest intense terrigenous input into the paleomire and a short distance from the sediment source region different mineralogical characteristics of the coals from the three mines datanhao hailiushu and adaohai of the daqingshan coalfield are probably due to the different source material in their respective surrounding subuplifts within the intermontane basin kaolinite displaying graupen tabular and vermicular textures and the common presence of quartz in the intra seam non coal bands from the datanhao coal seam indicate that most of these bands are tonsteins altered airborne volcanic ash the original magma is probably high level volatile rich silicic in composition

understanding the influence of slope on the threshold of coarse grain motion revisiting critical stream power abstract this paper investigates the slope dependent variation in critical mean bed shear stress for coarse grain motion and evaluates stream power per unit bed area as an alternative threshold parameter explanations for observed slope dependency and existing approaches for predicting the critical stream power per unit bed area are reviewed an analysis of secondary bed load transport datasets is used to examine the strength of associations between stream power per unit bed area mean bed shear stress and mean velocity with bed load transport rate data from an original flume study are combined with secondary data from similar flume experiments to investigate the effect of slope on both critical stream power per unit bed area and critical mean bed shear stress results suggest that stream power per unit bed area is most closely correlated with bed load transport rate and also that critical stream power per unit bed area is less variable with slope than critical mean bed shear stress alternative solutions to approximating critical stream power are explored these include 1 modifying existing expressions for critical stream power to account for higher critical mean bed shear stresses at higher slopes and 2 applying a constant dimensionless critical stream power criterion

river profiles along the himalayan arc as indicators of active tectonics abstract longitudinal profiles along sixteen major transverse himalayan rivers add important constraints to models of active continental subduction and its evolution these profiles are characterized by a zone of relatively high gradient that cannot be associated with differential resistence to erosion in all cases the base of the zone of increased gradients correlates with 1 the topographic front between the lesser and high himalayas 2 the narrow belt of intermediate magnitude thrust earthquakes 3 the main central thrust zone mct these features define a small circle in the central portion of the himalayan arc these correlations suggest that the discontinuity in the river profiles and the other features are controlled by a major tectonic boundary between the rising high himalayas and the lesser himalayas no sharp increases in gradient are observed near the main boundary thrust mbt except on a few rivers such as the jhelum or kundar where the mbt lies close to both the mct and the seismic belt thus it is unlikely that the mbt is a major tectonic boundary the diversion of river courses along the mbt and around anticlines in the sub himalayas has probably been caused by aggradation near the rosion deposition boundary upstream of uplifts in the mahabharat range and sub himalayas a parallel is drawn between the himalayas and new guinea based on the hypothesis that continent arc collision of the type occurring in northern australia preceded continent continent collision in the himalayas the present sedimentary tectonic phase in new guinea resembles the subathu paleocene eocene phase in the himalayas incipient counterparts of the major himalayan structures including the mct and the mbt are recognized in new guinea the drainage patterns in the himalayas and in new guinea bear a similar relation to major structures this suggests that 1 the tectonic evolution of the himalayas has been rather uniform since early stages of collision and 2 the himalayan drainage was also formed at these early stages and is therefore antecedent to the rise of the high himalayas

analysis origin and significance of mineral matter in coal an updated review abstract the material classed as mineral matter in coal embraces crystalline mineral materials as well as a range of inorganic elements that occur in non crystalline form this review outlines the methods that may be used to evaluate the percentage of mineral matter for a coal sample as opposed to the ash yield and to identify the minerals their individual percentages and their modes of occurrence within the coal the principal techniques include low temperature oxygen plasma ashing quantitative evaluation of x ray diffraction data observation using optical microscopy and a combination of observation chemical analysis and in some cases mapping based on scanning electron microscopy and related methods a range of other techniques may also be used to provide additional information on particular mineral matter components processes responsible for mineral matter formation include detrital input biogenic activity and authigenic precipitation at different stages of the coal s depositional and post depositional history differential migration of non mineral inorganic elements may also occur in lower rank coals and expulsion of non mineral inorganics may take place with rank advance knowledge of the mineral matter may be of assistance in understanding the modes of trace element occurrence with implications for assessing possible environmental impacts and also the potential for recovery of economic products from coal the behaviour of different mineral matter components at high temperatures is also discussed as well as methods for mineralogical analysis of ashes and other coal utilization products information from mineral matter studies may provide an improved basis for understanding coal formation and for evaluating the response of particular coals to different combustion gasification and coking processes

channel patterns braided anabranching and single thread a new channel pattern classification is presented based on theoretically derived channel pattern discriminant functions the thresholds are formulated as power laws that relate the critical slope associated with a change in channel pattern to dimensionless discharge and relative bank strength one threshold demarcates the boundary between stable single thread channels both straight and meandering and stable multiple thread channels anabranching another threshold separates anabranching from braided channels where braided channels are considered to be fundamentally unstable the exponents of the thresholds are nearly identical to that in the threshold equation originally proposed by leopold and wolman 1957 and the coefficients are quite similar as well an analysis of their data set using our dimensionless approach reveals that no fundamental difference exists between meandering and straight patterns and thus data from both types are grouped together under the more general heading of single thread channels furthermore we demonstrate that over a limited range of conditions an unstable single thread channel can form stable multiple threads but that for systems far from the threshold bounding the single thread channels the number of divisions required to produce stable anabranches grows geometrically this motivates a separation of multiple thread channels into anabranching and braided types our theoretical thresholds are then compared against several large data sets of field data and the results broadly confirm our proposed thresholds

theoretical development on the effects of changing flow hydraulics on incipient bed load motion 1 several decades of flume and field measurements have indicated that in rough turbulent flows the critical shields stress increases with increasing slope and associated decreasing relative depth this result contradicts the usual consideration of a decreased critical shields value on very steep slopes because of increased gravitational effects however recent studies have demonstrated that these experimental results could be reproduced with a force balance model if the classical logarithmic velocity profile was replaced with a velocity profile that was more compatible with available velocity measurements over gravel beds these measurements indicate the existence of a roughness layer that is a zone of almost constant velocity close to the bed whose properties mean velocity and turbulence depended on the flow s relative depth unfortunately velocity profile measurements for low relative depth associated with steep slopes are scarce and it is still difficult to include such flow properties in a force balance model flow resistance data on the basis of depth average velocity measurements are very common and cover a wide range of slopes and relative depths in this paper these data are used to fit a velocity profile including a roughness layer when used in a force balance model for incipient motion it adequately reproduced a data set composed of 270 critical shields values measured in a flume with near uniform sediments the relevance of this research to field problems is discussed using a data set composed of 92 critical shields stresses obtained from field measurements finally a model is proposed for field applications taking into account the slope effect

rare earth minerals in a no tonstein section of the dean fire clay coal knox county kentucky abstract the dean fire clay coal in knox county kentucky does not contain the megascopically visible ash fall tonstein present in most other sections of the coal bed like the fire clay tonstein a low ash portion of the coal is enriched in rare earth elements 2400 ppm on ash basis in addition to kaolinite produced in the diagenesis of volcanic glass transmission electron microscopy studies indicate the coal contains primary kaolinite la ce nd th monazite barium niobate native gold and fe ni cr spinels the mineral assemblages particularly the kaolinite monazite association and its similarity to the tonsteins in coal to the east demonstrate the coal was subject to the ree enriched volcanic ash fall apparently just at a more dilute level than at locations where the tonstein is present

assessment of downstream trends in channel gradient total and specific stream power a gis approach geographic information systems gis analyses of digital elevation models dems coupled with catchment area based discharge estimation techniques provide a relatively simple means of modelling contiguous downstream trends in channel gradient total stream power and in riverscapes conducive to regime analysis also specific stream power for a small high relief coastal catchment in se australia good agreement was obtained between channel gradients derived from a 25 m cell size dem and field survey equivalents over distances of several kilometres indicating that channel gradients derived from dems can have a reasonable degree of absolute as well as relative accuracy over multi kilometre reach scales assessment of downstream rates of change in channel gradient and specific stream power across four river systems suggests that some of the river reaches most responsive to high magnitude floods occur in zones where these variables rapidly decrease downstream modelling of downstream trends in channel gradient total and specific stream power from catchment wide dems has potential to provide a framework with which to investigate conceptual and empirical models between channel gradient stream power and the form and dynamics of river systems

the meandering braided river threshold a reappraisal abstract the concept of a threshold discharge slope q s combination that separates braided from meandering streams is critically re examined partly by review of previous data and partly by analysis of new data from south island new zealand it is argue d that discriminant functions that use mean annual discharge provide a poor physical basis for interpretations based on natural processes while bankfull discharge is also deficient because it is not a fully independent variable the common use of channel rather than valley slope adds a further misleading component because channel slope is partly dependent on channel pattern sinuosity most previous studies have inadequately treated the role of bed particle size in pattern discrimination failing to recognize that active gravel streams must plot higher on a q s chart than sand bed channels irrespective of pattern because of the greater power requirements for bed material movement within any one size class of bed material there is no evidence to indicate a clear discrimination between braiding and meandering only a weak statistical association between pattern and slope discharge values while this association may be explicable in terms of the high shear stress and stream power that accompany high qs values promoting braiding the real prerequisite for braiding appears to be high loads of bed calibre material producing wide shallow channels a factor that is only partly controlled by stream power accordingly the search for a pattern threshold based on discharge and slope seems to be a futile exercise an interpretation of existing pattern discriminant functions from the perspective of the threshold shear stress for particle movement is made it is concluded that in effect these functions merely state that gravel bed streams are more likely to be braided than channels in finer sediment statistically this appears to be valid and reasons for that difference are offered based on the balance between imposed bed material load and channel capacity

a provenance study of mineral matter in coal from appalachian basin coal mining regions and implications regarding the respirable health of underground coal workers a geochemical and nd isotope investigation abstract this study presents geochemical data produced from the analysis of coal and adjacent rock samples retrieved from coal mining regions in the u s to examine mineral matter provenance study sites included the northern appalachian basin where the units of interest were the lower kittanning coal bed the overlying columbiana shale and the underlying paleosol allegheny formation additional study sites were located in the central appalachian basin where sampling was conducted on strata associated with multiple coal beds of middle and lower pennsylvanian age the central appalachian basin rock and coal samples were much lower in overall mineral matter and contained very little carbonate calcite and siderite or pyrite mineralogy which was common at the northern appalachian basin sites elemental analysis of rock samples indicated a trend of enrichment in ca mg mn na and k cations in the immediate overburden compared to the underlying rock in the central appalachian basin a similar trend was observed in coal related strata from the northern appalachian basin which was attributed to epigenetic marine incursions rare earth element ree concentrations were determined in the samples and showed eu and ce anomalies when normalized by chondritic values the total ree content of the overburden is generally less than that of the underlying rock units neodymium isotopic analysis of the lower kittanning coal overburden and paleosol from the northern basin indicate partial resetting of the sm nd system close to the time of deposition the data indicate a common appalachian source for the clastic mineral matter in the overburden underclay and coal mineral matter the geochemical findings of this study may provide a viable method for distinguishing respirable dust sources in both appalachian basins there are potential applications for this research to aid in the respiratory health of underground coal miners

critical specific stream power in gravel bed rivers experiments with marked pebbles were carried out on different sized rivers of the belgian ardenne catchment areas varying from less than 1 km2 to 2700 km2 specific stream power required to cause bedload movement was evaluated and critical values were obtained three types of relationship between critical specific stream power 0 and grain size d were established the values for 0 in the largest river the ourthe were the lowest and were close to the values obtained for mountainous rivers carrying large boulders in medium sized rivers catchment area between 40 and 500 km2 the critical unit stream power was higher it is likely that it is due to the bedform s greater resistance this resistance would use up some of the energy that can cause movement and transport of bedload the amount of resistance of the bedform can be expressed as bedform shear stress determined by the relationship between grain shear stress that determines movement and transport of the bedload and the total shear stress this ratio varies between 0 4 and 0 5 in the medium sized rivers compared to 0 7 in the ourthe in headwater streams less than 20 km2 there is greater loss of energy due to bedform resistance 0 3 critical specific stream power is higher in this third type of river than in the other two

is the critical shields stress for incipient sediment motion dependent on channel bed slope data from laboratory flumes and natural streams show that the critical shields stress for initial sediment motion increases with channel slope which indicates that particles of the same size are more stable on steeper slopes this observation is contrary to standard models that predict reduced stability with increasing slope due to the added downstream gravitational force processes that might explain this discrepancy are explored using a simple force balance model including increased drag from channel walls and bed morphology variable friction angles grain emergence flow aeration and changes to the local flow velocity and turbulent fluctuations surprisingly increased drag due to changes in bed morphology does not appear to be the cause of the slope dependency because both the magnitude and trend of the critical shields stress are similar for flume experiments and natural streams and significant variations in bed morphology in flumes is unlikely instead grain emergence and changes in local flow velocity and turbulent fluctuations seem to be responsible for the slope dependency due to the coincident increase in the ratio of bed roughness scale to flow depth i e relative roughness a model for the local velocity within the grain roughness layer is proposed based on a 1 d eddy viscosity with wake mixing in addition the magnitude of near bed turbulent fluctuations is shown to depend on the depth averaged flow velocity and the relative roughness extension of the model to mixed grain sizes indicates that the coarser fraction becomes increasingly difficult to transport on steeper slopes

spatial analysis of stream power using gis slk anomaly maps the stream length gradient index sl shows the variation in stream power along river reaches this index is very sensitive to changes in channel slope thus allowing the evaluation of recent tectonic activity and or rock resistance nevertheless the comparison of sl values from rivers of different length is biased due to the manner in which the index is formulated thus making correlations of sl anomalies along different rivers difficult therefore when undertaking a comparison of sl values of rivers of different lengths a normalization factor must be used the graded river gradient k has already been used in some studies to normalize the sl index in this work we explore the relationships between the graded river gradient k the sl index and the stream power proposing the use of a re named slk index which enables the comparison of variable length rivers as well as the drawing of slk anomaly maps we present here a gis based procedure to generate slk maps and to identify slk anomalies in order to verify the advantages of this methodology we compared an slk map of the ne border of the granada basin with both simple river profile knickpoint identification and with an sl map the results show that the slk map supplies good results with defined anomalies and suitably reflects the main tectonic and lithological features of the study area copyright 2008 john wiley sons ltd

thresholds and the spatial variability of flood power during extreme floods abstract analysis of the effects of extreme events on overall landscape form has shifted geomorphic attention away from a focus on the magnitude and frequency relationship of discharge to a focus on flood power this paper analyzes the variation in flood power both at a station and downstream in a basin of differing lithologies and discusses the geologic and geomorphic controls on flood power design floods ranging from the 2 year discharge tothe 500 year discharge are routed trough a drainage basin and channel boundary shear stress and unit stream power are calculated using hec 2 along 21 cross valley transects because of the strong lithologic control on valley width and channel slope an irregular downstream pattern of flood power emerges which reflects primarily the pattern in valley width narrow valleys correspond to a greater percent of channel conveyance during large magnitude floods and increasing rates of depth increases thus maximizing flood power in these zones the opposite occurs in anomalously wide valleys where flood power is minimized a downstream spatial pattern emerges reflecting both local and general controls for a given probability event flood power varies at least threefold within the basin with a maximum occuring in a specific downstream section holding flood power constant produces an extremely wide range in flow probabilities in order to establish a link between critical flood power magnitude and flow frequency minimum flood powers are developed from an analysis of previous work on catastrophic flooding for humid alluvial channels these minimum thresholds tentatively correspond to 100 n m2 or 300 w m2 for shear stress and unit stream power respectively discharges required to attain these critical flood powers vary from events roughly twice the 100 year flood to a maximum of roughly 18 times the discharge of the 100 year flood

on the origin of the oak ridges moraine landscape analysis mapping sedimentology shallow geophysics and borehole data are integrated to better understand the complex landform sediment geometries and event sequences of the oak ridges moraine southern ontario a model for the origin of the oak ridges moraine is based on the recognition that the moraine is built on a high relief erosional surface unconformity consisting of drumlin uplands and a network of deep steep walled interconnected valleys tunnel channels the development of the moraine is thought to have occurred in four stages i subglacial sedimentation ii subaqueous fan sedimentation iii fan to delta sedimentation iv ice marginal sedimentation the model traces the transition from subglacial to proglacial conditions during moraine formation and examines the order and timing of sedimentation it is thought that the early stages of moraine construction are better exposed in the east in the west these stages are buried by later stages resume les etudes de paysage cartographie sedimentologie geophysique de subsurface et des carottes de trous des sondages ont ete menees conjointement pour chercher a mieux comprendre les configurations complexes des formes de relief sediments et les sequences des evenements qui ont affecte la moraine d oak ridges dans le sud de l ontario un modele interpretant l origine de la moraine d oak ridges est fonde sur le fait que cette moraine fut edifiee sur une surface d erosion discordance en terrain a topographie accentuee comprenant des drumlins sur terres elevees et des vallees a parois subverticales interconnectees chenaux tunnels le modele propose un developpement de la moraine en quatre phases i sedimentation sous glaciaire ii sedimentation d un eventail sous aquatique iii sedimentation de l eventail evoluant vers un depot deltaique iv sedimentation en bordure d un glacier le modele retrace la transition de conditions sous glaciaires a proglaciaires durant la formation de la moraine et traite de l ordre et de la chronologie du sediment il apparait que c est dans le secteur oriental que les premieres phases de l edification de la moraine sont le mieux exposees tandis que dans le secteur partie occidental elles sont enfouies sous le sediment des phases plus tardives

downstream variation in bankfull width of wadeable streams across the conterminous united states abstract bankfull channel width is a fundamental measure of stream size and a key parameter of interest for many applications in hydrology fluvial geomorphology and stream ecology we developed downstream hydraulic geometry relationships for bankfull channel width w as a function of drainage area a w a dhg wa for nine aggregate ecoregions comprising the conterminous united states using 1588 sites from the u s environmental protection agency s national wadeable streams assessment wsa including 1152 sites from a randomized probability survey sample sampled stream reaches ranged from 1 to 75 m in bankfull width and 1 to 10 000 km 2 in drainage area the dhg wa exponent which expresses the rate at which bankfull stream width scales with drainage area fell into three distinct clusters ranging from 0 22 to 0 38 width increases more rapidly with basin area in the humid eastern highlands encompassing the northern and southern appalachians and the ozark mountains and the upper midwest great lakes region than for the west both mountainous and xeric areas the southeastern coastal plain and the northern plains the dakotas and montana stream width increases least rapidly with basin area in the temperate plains cornbelt and southern plains great prairies in the heartland the coefficient of determination r 2 was least in the noncoastal plains 0 36 0 41 and greatest in the appalachians and upper midwest 0 68 0 77 dhg wa equations differed between streams with dominantly fine bed material silt sand and those with dominantly coarse bed material gravel cobble boulder in six of the nine analysis regions where dhg wa equations varied by sediment size fine bedded streams were consistently narrower than coarse bedded streams within the western mountains ecoregion where there were sufficient sites to develop dhg wa relationships at a finer spatial scale and ranged from 1 23 to 3 79 and 0 23 to 0 40 respectively with r 2 0 50 for 10 of 13 subregions range 0 36 to 0 92 enhanced dhg equations incorporating additional data for three landscape variables that can be derived from gis mean annual precipitation elevation and mean reach slope significantly improved equation fit and predictive value in several regions most notably the western mountains and the temperate plains channel width was also related to human disturbance we examined the influence of human disturbance on channel width using several indices of local and basinwide disturbance contrary to our expectations the data suggest that the dominant response of channel width to human disturbance in the united states is a reduction in bankfull width in streams with greater disturbance particularly in the western mountains where population density road density agricultural land use and local riparian disturbance were all negatively related to channel width and in the appalachians and new england where urban and agricultural land cover and riparian disturbance were all negatively associated with channel width

geochronology and tectonic setting of silicic dike swarms and related silver mineralization at candelaria western nevada the candelaria mining district in central western nevada preserves a record of tectonism magmatism and mineralization related to early mesozoic development of the cordilleran magmatic arc a deformed basement of ordovician chert phyllite palmetto complex and its thin parautochthonous cover of permo triassic marine clastic rocks diablo and candelaria formations are structurally overlain along the pickhandle golconda thrust system by ophiolitic tectonic melange forming the base of the golconda allochthon the total assemblage is cut by three overlapping swarms of silicic dikes comprising from the oldest to the youngest fine grained sparsely porphyritic calc alkaline rhyolites medium grained strongly porphyritic high k calc alkaline dacites fine grained calc alkaline rhyolites u pb zircon dating gives ages of 222 or 2 ma for the older rhyolites 192 or 3 ma for the porphyries and 196 or 24 ma for the younger rhyolites these swarms are products of the triassic jurassic cordilleran magmatic arc which developed under a long lived broadly extensional to transtensional tectonic regime to generate a major intra arc graben system characterized by voluminous caldera related ignimbrites the dike swarms possibly mark the site of an eroded caldera the dacite porphyries are genetically associated with important sediment hosted disseminated silver gold base metals mineralization which occurs in thick tabular zones along the pickhandle thrust and in a subparallel footwall structure the lower candelaria shear which cuts reactive carbonaceous marly shales at the base of the candelaria formation mineralization occurs where the porphyries intrude the pickhandle thrust and the lower candelaria shear the 192 or 3 ma date for the dacites defines candalaria as the oldest disseminated precious metal deposit in the great basin there are similarities in tectonic setting magmatic association metal composition and possibly age between candelaria and the darwin type pb ag zn vein replacement deposits of southeastern california differences in host rock composition and host rock amenability to structural preparation may account for grade tonnage differences between candelaria large low grade hosted by thin bedded marly shales and the darwin type deposits small high grade hosted by more massive carbonate rocks k ar ages for sericites from the hydrothermal alteration envelope at candelaria range from 91 to 132 ma mid to late cretaceous the discrepancy between these ages and those of the silicic dikes is attributed to regional scale reheating and resetting of k ar isotopic systematics related to development of the younger crosscutting jurassic cretaceous cordilleran magmatic arc this arc generated the sierra nevada batholithic belt which is represented locally by several small calc alkaline granite porphyry stocks dated at 84 to 97 ma k ar biotite exposed within a few kilometers of candelaria

geochemistry of late triassic coals in the changhe mine sichuan basin southwestern china evidence for authigenic lanthanide enrichment abstract five thin coals of late triassic age occur in the changhe mine sichuan basin southwestern china petrology and geochemistry of these coals and their roof parting and floor samples were studied the results show that the changhe coals are enriched in as 8 9 11 8 g g w 2 2 11 2 g g pb 20 8 48 2 g g and th 7 5 18 8 g g the source of these elements is possibly the xuefeng old land which is an early paleozoic source area southeast of the sichuan basin two tonsteins were found in the changhe mine one is the roof k8r of the k8 coal which is a pure kaolinitic claystone the other is the claystone k9c above the roof of the k9 coal which is mainly made up of mixed illite smectite minerals the ree content 287 9 g g of the k8 coal is much higher than that of its roof 153 6 g g sem edx results show that authigenic monazite and kaolinite are the main carriers of ree in the k8 coal on the basis of coal chemistry and occurrence of the precipitated minerals it is likely that leaching of the k8r tonstein occurred it is possible that trace elements including be 8 4 g g zr 302 g g nb 26 g g hf 9 7 g g th 18 8 g g u 5 8 g g ga 16 1 g g and pb 48 2 g g in the k8 coal were also elevated by the leachate of its overlying tonstein k8r the k9c tonstein with a total thickness of 16 cm is widely distributed in the changhe mine and serves as a distinct marker bed for correlation of coal seams besides mixed illite smectite minerals trace amounts of euhedral zircon anatase apatite and massive silica with vesicular structure were also examined these constitute strong evidence for its felsic volcanic ash origin

origin and interpretation of knickpoints in the big south fork river basin kentucky tennessee this study investigates the causes of knickpoints and knickzones in the bedrock controlled streams of the big south fork river basin in kentucky and tennessee knickpoints in the big south fork river area vary in form and apparent origins while some are likely related to base level change and incision in the cumberland river drainage system the locations and drainage relations of the knickpoints are not consistent with transmission of an incision signal throughout the network local controls predominate in forming steeper channel segments with no single factor dominant knickpoints in the study area are characterized by polygenesis and multiple causality though several archetypes can be identified these include rock fall rapids created by mass wasting from adjacent valley slopes structurally controlled headwater cliffs and lithological knickpoints a fourth category local incision knickpoints may be attributable to a variety of factors influencing force resistance relationships these results imply that the simple presence of a knickpoint cannot be attributed to any particular cause or history without consideration of the local controls this further implies that factors such as the spacing of knickpoints may not be an indication of migration rates or that migration has even occurred however the analysis of individual profile convexities can shed light on various controls such as lithology and structure and other processes such as valley side mass wasting and local bed incision important in evolution of fluvially dissected landscapes

an automated method for producing synoptic regional maps of river gradient variation procedure accuracy tests and comparison with other knickpoint mapping methods abstract the study of abrupt changes in longitudinal river profiles or knickpoints is currently approached through an empirical power law the slope area relationship results based on digital elevation model dem analyses and stream extractions are generally intended to determine crustal uplift rates and identify transient landscape conditions in this article we present an alternative geomorphometric method for locating knickpoints and knickzones based on local slope gradient and curvature attributes intended as a rapid regional scale automated knickpoint detection technique the accuracy of this slope curvature method is tested on two digital elevation grids nasa s srtm ground resolution of 90 m resampled here to 75 m and the aster dem 15 m in the sierra nacimiento new mexico usa a basement cored mountain range recently exhumed by waves of headward drainage integration in response to remote tectonic deformation in the adjacent rio grande rift out of every 10 gradient anomalies detected by the srtm derived numeric routine up to 8 are certifiable knickpoints recognized among a population of georeferenced occurrences surveyed in the field an independent comparison with the slope area method provided a further accuracy test which was particularly useful at sites that could not be validated in the field for practical reasons given the low tectonic activity of the study area the majority of knickpoints was also found to coincide with lithologic boundaries making it difficult without further geomorphological data to single out dynamic knickpoints directly caused by the upstream propagation of channel instabilities relating to base level change

downstream variation in stream power abstract stream power has a significant influence on many form and process attributes of the fluvial system using a similar approach to that suggested by d m lawler in 1992 and 1995 a model is developed to explore how stream power might vary in the downstream direction based on the assumption that the longitudinal profile of the river has an exponential form no particular discharge is necessarily specified but near bankfull flows are regarded as significant morphologically and one such discharge is the focus here total stream power per unit channel length qs is predicted to peak at an intermediate location the position of which depends on the ratio b where b and are the downstream rates of change of discharge and slope respectively if b is a relatively conservative quantity then the form of the longitudinal profile and in particular its degree of concavity will have the major influence on the position of maximum stream power specific stream power w is even more sensitive to and is expected to peak closer to the headwaters about half way between source and the location of the stream power maximum although this will depend on how channel width w varies with distance from source the model is tested along three connected streams of different size in the catchment of the river trent taking advantage of a relationship between mean annual flood and link magnitude which enables this near bankfull discharge to be estimated at any point within the network the model is verified in so far as stream power does attain a mid basin maximum but the observed and predicted locations of the maxima do not always correspond largely because of the distinctive variation in discharge and especially slope along individual pathways for example maximum power lies far downstream along the trent because of the large increase in mid basin discharge associated with a series of large closely spaced tributaries the importance of slope is borne out by the near headwater locations for specific power maxima which tend to be further upstream than predicted along all three rivers as a result of the steepness of upper reaches the variety of geomorphic settings produces deviations from expectation which has implications for the movement and storage of material in the fluvial system

glacial erosion evolution of river long profiles and the organization of process domains in mountain drainage basins of coastal british columbia 1 in glaciated british columbia canada quaternary climate changes are responsible for profound spatial reorganization of earth surface processes these changes have left a landscape characterized by topographic anisotropy associated with a hierarchy of glacial troughs the evolution of glaciated landscapes is examined by analyzing the structure of geomorphic process domains and channel long profiles to identify process domains we use channel surveys and gis analysis to construct slope area transects of the channel network this analysis reveals generalized process form disequilibrium with a mismatch between topographic signatures and currently active geomorphic process domains at the landscape scale of source colluvial channels contributing area 1 km2 the glacial paraglacial signature commonly overrides that produced by contemporary debris flows along the axis of former ice flows relict glacial cirques introduce a hanging fluvial domain at contributing areas as small as 8 10 2 km2 and produce complex channel long profiles similar to those observed for rivers responding to tectonic forcing slope area relations typical of unglaciated equilibrium environments do not apply here the concept of process domains appears to hold however some major glacially forced modifications in the alluvial colluvial transition are observed and the definition of a depositional colluvial subdomain is proposed comparison between field and gis measured slopes reveals that gis associated error is not uniform between process domains and that gis based plots do not successfully discriminate field based process domains the combination of glacial and post glacial fingerprints and the effects of ongoing earth surface processes generate a complex landscape whose glacial signatures may persist until the onset of the next ice age

bedload entrainment in low gradient paraglacial coastal rivers of maine u s a implications for habitat restoration abstract the rivers of coastal maine flow through mainstem lakes and long low gradient reaches that break the continuum of bedload transport expected in nonparaglacial landscapes stream erosion of glacial deposits supplies coarse sediment to these systems the land use history includes intensive timber harvest and associated dam construction which may have altered the frequency of substrate mobilizing events these watersheds are vital habitat for the last remaining wild anadromous atlantic salmon in the united states future adjustments in channel morphology and habitat quality via natural stream processes or restoration projects depend on erosion transport and deposition of coarse sediment these factors motivate our study of competence at four sites in the sheepscot and narraguagus watersheds three of the four sites behaved roughly similarly with particle entrainment during intervals that include winter ice and spring flood conditions and relatively minor bed mobilization during moderate floods in the summer and fall with a recurrence interval of 2 3 years the fourth site on the sheepscot river mainstem exhibits more vigorous entrainment of marked particles and more complex three dimensional channel morphology this contrast is partially due to local geomorphic conditions that favor high shear stresses particularly relatively steep gradient but also likely to nourishment of the bedload saltation system by recruitment from an eroding glacial deposit upstream our results suggest that the frequency and magnitude of bedload transport are reach specific depending on factors including local channel geometry upstream sediment supply and transport and formation of anchor ice this presents a challenge for stream practitioners in this region different reaches may require contrasting management strategies our results underscore the importance of understanding channel processes at a given site and assessing conditions upstream and downstream as a prerequisite for conducting habitat restoration projects

an analogue of dominance of tectonic over climatic forcing in intermontane coal bearing basins padul se spain abstract a multiproxy study based on sedimentology mineralogy magnetic susceptibility organic geochemistry and fossil content allowed to establish the sedimentary evolution of palustrine basins and to study the interplay between tectonic and climatic forcings in the sedimentation and facies arrangement that can be extrapolated to other coal bearing basins the reinterpretation of the data from 18 cores allowed to determine the facies distribution and to model the sedimentary evolution of the padul basin with the longest continuous continental quaternary record in the southwestern mediterranean region the padul basin sediment record and facies successions provide an outstanding example of tectonically and environmentally controlled sedimentation the sedimentary characteristics of the cores and thickness distribution revealed that recent tectonics was a more important forcing than other processes e g climate the influence of recent tectonics was determinant in facies arrangement that is to say that the activity of a rotated fault produced a differential subsidence causing more than 100 m of palustrine deposits to stack on the basis of the sedimentological record combined with data on the mineralogy fossil content magnetic susceptibility and total organic carbon three main sedimentary units were identified linked to diverse subsidence rates and paleoenvironmental oscillations the magnetic susceptibility was likely to have been controlled by the organic matter content toc values linked to oxic anoxic conditions in the lower part of the record unit a 107 0 68 7 m shallow lacustrine conditions were dominant with an important influx associated with considerable runoff from active alluvial fans linked to a higher subsidence rate unit b 68 7 37 6 m had a transitional character with a considerable decrease in the influence of the alluvial fan system the lake recharge through overland flow markedly diminished and pre existing groundwater recharge was dominant a sudden change to peaty materials indicated that surface runoff was directly diverted to the recently excavated durcal river gorge thereby precluding the basin from becoming a swampy environment with stagnant waters unit c upper 37 6 m was almost exclusively fed by bicarbonate groundwater and subsurface runoff through the highly permeable coarse alluvial fan deposits within these main sedimentary units minor mud peat shallowing upward sequences were identified

elements and phosphorus minerals in the middle jurassic inertinite rich coals of the muli coalfield on the tibetan plateau abstract the content modes of occurrence and origin of elements and phosphorus minerals in the jurassic coals of the muli coalfield on the tibetan plateau were investigated using optical microscopy field emission scanning electron microscopy in conjunction with energy dispersive x ray spectrometry x ray powder diffraction x ray fluorescence spectrometry and inductively coupled plasma mass spectrometry the muli coals l1 and l2 coals are of high volatile a bituminous to medium volatile bituminous rank characterized by low sulfur contents and are generally dominated by the inertinite group macerals predominantly semifusinite and fusinite the l1 coal contains abundant apatite 7 9 on average on an organic matter free basis and alumino phosphate minerals of goyazite gorceixite crandallite group 4 9 on average and accordingly the concentrations of elements f 253 g g on average p 2349 g g sr 526 g g and ba 790 g g are elevated as compared with common world hard coals the deposition of phosphorous bearing minerals in the muli coals was not derived from volcanic input penetration of ca and al rich solutions release of phosphorus from organic matter during plant decay and an appropriate sedimentary environment such as low ph low water table for peat and oxidizing conditions were critical factors in deposition of the phosphorus minerals

lanthanide yttrium and zirconium anomalies in the fire clay coal bed eastern kentucky abstract the fire clay coal bed in the central appalachian basin region contains a laterally persistent tonstein that is found in the coal throughout most of its areal extent the tonstein contains an array of minerals including sanidine quartz anatase and euhedral zircon that constitutes strong evidence for a volcanic origin of the parting for this study five samples of the tonstein and four sets of coal samples underlying the tonstein were collected from five sites in eastern kentucky inductively coupled plasma mass spectroscopy icp ms analysis of the tonstein and underlying coal collected from four sites in eastern kentucky show that although zr concentrations are high in the tonstein 570 1820 ppm on a coal ash basis cab they are highest in the coal directly underlying the tonstein 2870 4540 ppm cab a similar enrichment pattern is observed in the concentration of y plus the sum of the rare earth elements y ree total y ree concentrations in the five tonstein samples range from 511 to 565 ppm cab however y ree contents are highest in the coals directly underlying the tonsteins values range from 1965 to 4198 ppm cab scanning electron microscopy of samples from coal which directly underlies two of the tonstein samples show that ree rich phosphate tentatively identified as monazite commonly infills cracks in clays and cells in clarain and vitrain zircon is rare and commonly subhedral on the basis of coal chemistry and grain morphology we suggest that volcanic components in the tonstein were leached by ground water the leachate rich in y and ree precipitated as authigenic mineral phases in the underlying coal

geochemical and mineralogical anomalies of the late permian coal in the zhijin coalfield of southwest china and their volcanic origin abstract this paper describes the influence of volcanic ash on the concentrations and occurrences of associated elements in coal in the zhijin coalfield in western guizhou province china our studies reveal that the no 9 coal seam in the zhijin coalfield has very high content of fe 4 34 cu 369 90 g g u 49 6 g g mo 63 10 g g zn 33 97 g g and zr 841 80 g g the studies have also found that elements such as fe and cu do not occur as sulfides in this coal seam in sharp contrast to many other coal seams in china the geochemical and mineralogical anomalies of the coal seam are attributed to synsedimentary volcanic ash in addition to normal macerals and minerals in coal a volcanic influenced material vim derived from volcanic ash detrital material of terrigenous origin and organic matter was identified under polarized light reflectance microscopy and scanning electron microscopy equipped with energy dispersive x ray edx analyzer the volcanic influenced material is the main carrier of the above elements in this coal six types of the volcanic influenced material vim 1 vim 2 vim 3 vim 4 vim 5 and vim 6 are further distinguished on the basis of their structures and compositions to the best of our knowledge this is the first report that presents a detailed classification of coal components with a high content of volcanic ash

a review of anomalous rare earth elements and yttrium in coal abstract coal deposits have attracted much attention in recent years as promising alternative raw sources for rare earth elements and yttrium rey not only because the rey concentrations in many coals or coal ashes are equal to or higher than those found in conventional types of rey ores but also because of the world wide demand for rey in recent years has been greater than supply in addition to anomalies of enrichment or depletion of light medium and heavy rey in coal deposits normalized to upper continental crust post archean australian shale or north american shale composite anomalies of redox sensitive ce and eu and in some cases of non redox sensitive la gd and y could be used as geochemical indicators of the sediment source region sedimentary environment tectonic evolution and post depositional history of coal deposits factors controlling rey anomalies in coal deposits include the geochemistry of terrigenous source rocks ingress of hydrothermal fluids influence of marine environments percolating natural waters volcanic ashes and sedimentary environments of peat formation additionally the smoothness of a normalized rey distribution pattern provides a simple but reliable basis for testing the quality of rey chemical analyses for coal and other sedimentary rocks

spatial organization of process domains in headwater drainage basins of a glaciated foothills region with complex longitudinal profiles 1 lithologic transitions and glaciations create complex longitudinal profiles that control contemporary erosion and deposition processes in areas with these characteristics traditional morphometric approaches for predicting process domains such as area slope plots can be augmented by considering other predictors measured from high resolution lidar derived digital elevation models dems ordinal logistic regression was used to model the distribution of hillslope swale colluvial channel and fluvial channel domains as identified during field surveys the study area was a glaciated region of the rocky mountain foothills with a complex lithostructural setting relationships between domains and a suite of geographic information system derived descriptors were explored predictors included profile anomalies measured at the reach and basin scale using a normalized stream length gradient sl k index drainage area was the dominant factor controlling domains a model with area as the only predictor was 82 accurate reach slope relations were not consistent a model that also included lithology and basin scale sl k index variation was 87 accurate domain transitions had larger area thresholds in basins with resistant conglomerate versus sandstone or shale formations and where sl k index was more variable along a profile in a restricted model of hillslope swale and colluvial channel domains profile curvature measured over 100 m was also related to domain occurrence a model for regional scale mapping applications with six additional predictors was 95 accurate the results showed that ordinal logistic regression can be used to predict and map process domains in regions with complex physiography using descriptors measured from high resolution dems

mineralogy of the volcanic influenced great northern coal seam in the sydney basin australia abstract the mineralogy of the individual coal plies and intra seam claystone bands in the great northern seam of the sydney basin has been evaluated using optical and scanning electron microscopy and quantitative x ray diffraction techniques the uppermost two claystone bands are tonsteins consisting mainly of well ordered kaolinite with graupen to vermicular textures idiomorphic crystals of k feldspar within these tonsteins may represent members of the anorthoclase sanidine series or a sodic sanidine and indicate an acid to intermediate volcanic ash input in contrast the lowermost parting was largely derived from epiclastic sediment admixed with minor volcanic material such as high temperature quartz and a different type of k feldspar component the mineral fraction of the coals especially in the middle and upper parts of the seam is dominated by authigenic kaolinite with a very low abundance of quartz apart from the tonsteins authigenic processes therefore appear to be the dominant mechanism of mineral matter formation authigenic k feldspar also occurs in the lower few metres of the seam with a variety of modes of occurrence including cell and cleat infillings cross cutting veins and thin laminae parallel to the organic matter and detrital clay bands a late syngenetic low temperature hydrothermal fluid injection process is suggested for formation of the feldspar veins the origin of the fluid is uncertain but is most likely associated with contemporaneous volcanic activity

volcanic emission of se te and as from kilauea volcano hawaii abstract the se te and as content of the eruptive gas and of sulfur sublimates from the current jan 1983 through mar 1985 east rift eruption of kilauea volcano hawaii have been determined these data in combination with previous data suggest that most of the se and te in eruptive plumes occur in the particulate fraction while most of the as is in the gas phase eruptive emissions to the atmosphere have been estimated at 10 metric tons each of se and as and 2 tons of te over the first 14 months of the eruption material balance calculations suggest 0 28 ppm se and 0 017 ppm te for the initial kilauean magma content of these elements only one third of the original se and te is lost from the magma by degassing

factors affecting the geochemistry of a thick subbituminous coal bed in the powder river basin volcanic detrital and peat forming processes abstract the inorganic geochemistry and mineralogy of three cores from the anderson dietz 1 coal bed a 15 2 m thick subbituminous coal bed in the tongue river member paleocene of the fort union formation were examined 1 to determine if the cores could be correlated by geochemical composition alone over a total distance of 2 km and 2 to identify the major factors that influenced the geochemistry of the coal bed chemical data 46 elements on a coal ash basis for 81 coal samples and 4 carbonaceous rock samples with most samples representing a 0 6 m thick 2 ft interval of core were grouped into compositional clusters by means of cluster analysis seven major clusters were produced two of these clusters can be used to correlate the coal bed throughout the study area data from scanning electron and optical microscope analyses indicate that several factors influenced the geochemistry of the anderson dietz 1 coal bed the majority of mineral grains in the coal bed are interpreted to be detrital water borne evidence includes the presence of rounded to subrounded quartz grains having two phase aqueous fluid inclusions characteristic of hydrothermal or low to moderate grade metamorphic quartz these quartz grains are found throughout the coal bed but are most abundant in samples from the midpart of the bed which was influenced by detrital input associated with the deposition of the clastic rocks that form the split between the anderson and dietz 1 coal beds 900 m to the east of the study area in addition to the detrital minerals mentioned above volcanic ash that was fluvially transported to the sites of peat deposition or possibly deposited as air fall volcanic ash also affected the geochemistry of the coal bed for example crandallite a mineral reported to form as an alteration product of volcanic ash is found in seven samples from the coal bed the presence of quartz grains containing silicate melt inclusions in eight samples from the coal bed provides further support for a volcanic ash component other factors that probably affected the geochemistry of the coal bed include 1 detrital input associated with the deposition of the roof rocks of the coal bed 2 peat forming processes and plant material and 3 epigenetic ground water flow

estimating critical stream power for bedload transport calculations in gravel bed rivers the physical basis of bagnold s equation for critical stream power is examined although the general approach is well founded the original equation can be criticised for 1 failing to distinguish between the grain size in transport and the grain size that represents bed roughness 2 requiring a knowledge of critical flow depth in addition to gross channel properties 3 failing to allow for hiding and protrusion effects on the mobility of mixed size stream beds more general equations are presented which overcome these limitations they require a knowledge of channel slope but not depth the analysis suggests that the presence of form resistance in addition to grain roughness does not affect the calculation of critical power critical power is expected to depend more sensitively on grain size between reaches than within reaches

causes of concavity in longitudinal profiles of rivers a smooth concave configuration represents the most common quasi equilibrium profile of alluvial rivers in the present paper a generalized unified set of models for the longitudinal profile of rivers is presented various independent effects that drive concavity in longitudinal rivers are considered and classified the driving mechanisms considered here are 1 horizontal wavelike progradation of the river profile 2 abrasion of bed particles 3 aggradation of the river profile balancing subsidence at a constant speed and 4 the effect of tributaries adding sediment and water to the main stem of the river for simplicity it is assumed that the long term supply of water and sediment is constant hence a single discharge that is bank full discharge is used as an approximate characterization of the hydrologic regime for each point along the river sediment sorting has been studied elsewhere and is excluded from this analysis the river is assumed to have uniform bed material although the mean size may vary downstream it is concluded that the quasi equilibrium longitudinal profile created by each of the first three driving mechanisms mentioned above is concave the degree of concavity varies however depending on a set of physical conditions that can be identified by a set of dimensionless numbers a comparison of these numbers reveals the relative importance of the driving mechanisms for concavity a condition for concavity driven by the fourth mechanism that is tributary input is delineated