genetic classification of polish lignite deposits a review abstract poland is one of the largest lignite producers not only in the european union but also in the world the majority of lignite deposits that have economic value are of early and middle miocene age however the early oligocene lignite seam and the so called accompanying lignite seams of middle miocene age may also occasionally be important for the mining industry therefore five main and two accompanying lignite seams are described among the oligocene miocene sediments in central western poland these seams are present in sixty nine deposits which are taken into consideration in this contribution polish lignite deposits can be classified genetically thus they are divided into four main types epeirogenic tectonic karstic and glaciotectonic which contain seven subtypes sheet lenticular grabens salt karst carbonate karst fold thrust sliced of lignite deposits the vast majority of lignite resources represent the tectonic and or epeirogenic type of deposits almost 100 of lignite production in poland that is about 63 66 mt per year is exploited from them on the other hand the most deformed syn and or post depositionally are two deposits the rogo no and sieniawa ones which belong to the salt karst type salt karst subtype and the glaciotectonic type fold and thrust sliced subtypes of lignite deposits respectively finally knowledge about the genesis of lignite deposits can be useful during their exploration and exploitation this allows for proper planning of geological prospecting of the deposits and the use of a better method of lignite mining

proterozoic mafic ultramafic intrusions in the arunta region central australia part 2 event chronology and regional correlations abstract the arunta region in central australia records multiple proterozoic crustal processes over a 1500 million year period the timing of mafic ultramafic magmatism in this evolution is constrained by shrimp u pb dating of zircon which is a primary phase in mafic ultramafic intrusions across the region the earliest mafic magmatism was part of the 1810 1800 ma stafford event and a second episode is recognised during the 1790 1770 ma yambah event zircon overgrowths in some of these early intrusions record metamorphism during the strangways event a regionally pervasive metamorphic episode whose termination at ca 1690 ma coincided with intrusion of dolerite dykes gabbro intrusion during the ca 1640 ma liebig event is related to the geologically distinct warumpi province in the south of the region there is no record of mafic magmatism during the ca 1590 ma chewings event later systems include the ca 1130 ma alkaline ultramafic mordor complex and basaltic bodies are components of the irindina province which experienced high grade metamorphism during the palaeozoic the dating associates mafic ultramafic magmatism with each of these events which suggests that repeated extensional systems are an important aspect of the tectonic evolution the example of routinely obtaining zircon for dating from mafic and even ultramafic intrusions using an integrated approach of field and geochemical criteria to guide sampling opens the possiblility of dating mafic ultramafic intrusions elsewhere direct dating of mafic ultramafic magmatism permits its significance in proterozoic event systems to be evaluated directly free of assumed or conjectural timing correlations with the felsic plutons that are more often studied for age control

chronology of late wisconsinan glaciation in middle north america abstract we propose a chronology of late wisconsinan glacial fluctuations in middle north america from alberta to wisconsin based on radiocarbon dates derived solely from wood previous chronologies of the southwestern margin of the north american continental ice sheet have depended to a considerable degree on radiocarbon dates from fine grained organic sediment this material is commonly contaminated with older carbon resulting in chronologic confusion by using only dates from wood much of the confusion disappears however because of the scarcity of wood dates only four of the sixteen identified fluctuations are accurately dated an advance into iowa about 14 000 to 13 500 bp an advance into south dakota and iowa about 12 300 bp an advance into the lake michigan basin about 11 700 bp and an advance into the lake superior basin about 9900 bp in addition the beginning of late wisconsinan glaciation before 20 000 bp is fairly well documented none of the fluctuations in the western part of the region are accurately dated

hydrologic connectivity of oxbow lakes along the lower guadalupe river texas the influence of geomorphic and climatic controls on the flood pulse concept summary hydrologic connectivity between rivers and floodplains is fundamental to the ecological integrity of meandering river corridors this study integrates two important concepts in floodplain hydrology the flood pulse concept and the oxbow lake cycle high temporal resolution 0 5 3 0 h lake level data from vented pressure transducers and river discharge data 0 25 h resolution were utilized to develop standardized indices of hydrologic connectivity for two oxbow lakes along the lower guadalupe river texas over a 3 4 yr period the lakes were influenced by hydrologic conditions representative of the northwestern gulf region notably a severe drought and a wet season associated with la nina and el nino respectively because the data were obtained over the same period it enables a direct comparison of surficial hydrologic connectivity within the evolutionary geomorphic framework of the oxbow lake cycle a recently 13 yr old formed oxbow lake was connected 5 9 times per yr and an older partially infilled oxbow lake was connected 3 8 times per yr during the study period each oxbow lake was connected by discharge pulses below bankfull discharge and the signature of hydrologic connectivity varied significantly the flow duration for connectivity was 18 and 3 for the recently formed and older oxbow lake respectively bivariate relations between discharge and lake stage varied significantly for the two oxbow lakes the recently formed oxbow lake exhibited highly linear relations between discharge and lake levels and lake drainage closely mirrored flood wave recession older oxbow lake connectivity was complex as discharge and lake level relations were nonlinear and exhibited pronounced negative hysteresis which increased with sequential flood pulses while the older oxbow lake was more sensitive to short term low flow conditions both lakes were completely desiccated during an extended la nina influenced drought this indicates a substantial impact to alluvial aquifers which were unable to supply groundwater to oxbow lakes during extended dry periods the flood pulse concept applied with only river discharge data is overly simplistic and does not adequately characterize hydrologic connectivity for distinct types of oxbow lakes along meandering river floodplains with limited lake level data however great potential exists for development of effective integrated floodplain management plans that more appropriately considers variable hydrologic connectivity inherent within the oxbow lake cycle

fault reactivation and superimposed folding in a proterozoic sandstone volcanic sequence davenport province central australia abstract the davenport province is a fluvial to shallow marine sequence of weakly metamorphosed sandstone rhyolite and basalt deposited in an ensialic basin that was probably initiated by continental extension isopach ridges and cut offs suggest that synsedimentary normal and transfer faults controlled deposition these faults were reactivated as reverse faults and strike slip faults during deformation upright concentric folding took place in two episodes initially about nw trending axes and subsequently about generally ne trending axes balanced cross sections suggest that the folds die out downwards above the base of the sequence however units from well below the concentrically folded part of the sequence crop out in anticlinal cores indicating that there is no through going detachment horizon in the sequence this is consistent with the rarity of clayey silty and evaporitic sediments suitable for detachment hence the faults probably cut the entire sequence and enter the basement interference of the folds formed dome and saddle and crescentic patterns thrust sheets imbricate stacks and duplexes are not recognized in the province and layer parallel shortening is moderate about 28 these suggest a correspondingly low degree of earlier regional extension about 40 the folding may have been due to a sudden change in lithospheric plate velocity

spatial variation in the power of mountain streams in the sangre de cristo mountains new mexico the principle indicator of river energy expenditure stream power has a significant influence on many forms and process attributes of the fluvial system yet few basin wide analyses of stream power variations have ever been conducted recent studies hypothesize a peak in the mean stream power distribution in small 10 km2 to intermediate 100 km2 sized basins to test hypothetical stream power profiles in a high mountain setting 129 cross sections of stream networks within the costilla basin of northern new mexico and southern colorado were measured for channel form local sediment conditions and basin characteristics geomorphic and hydrologic analysis of these river sites throughout the costilla basin yielded evidence of abundant local control over fluvial processes and forms within the basin the spatial deviations of stream power from the hypothetical patterns derived from hydraulic geometry in some cases 200 deviation match areas of specific geologic and hydrogeologic control as an alternative to traditional hydraulic descriptions of downstream channel form a probabilistic process response model can incorporate local and basin scale variables and allow more realistic feedback mechanisms than in traditional regime theory the probabilistic nature of this type of model also allows prediction of multiple modes of channel adjustment an ever present challenge to extremal and physically based simulations

distribution diversity and geomorphic evolution of floodplain wetlands and wetland complexes in the ganga plains of north bihar india abstract floodplain wetlands are important features in alluvial settings across the world because of their ecological and hydrological significance understanding the geomorphic evolution of such wetlands is therefore not only interesting from an academic viewpoint but also necessary for their conservation and protection using a hierarchical system of geomorphological elements and units detailed geomorphic investigations have been carried out in the kosi ganga interfluve eastern ganga plain egp in the himalayan foreland to understand the distribution and diversity of the floodplain wetlands in this region the major geomorphic elements in this region consisting of lentic wetlands lakes and lotic streams water bodies were mapped using multispectral satellite images the distribution of the wetlands analysed through chord diagrams suggests that these are highly localised and associated with the regional geomorphic setting and the fluvial dynamicity the morphometric characterisation of these wetlands using their count area average area and total area shows significant variability among the geomorphic units the equal area circle eac such as the shoreline development index dl was found to be inadequate to assess the geomorphic maturity of the lentic water bodies and hence a new maturity index mch has been designed in this work using the convexity and area of the water bodies further the space for time substitution approach has been used to develop the evolutionary pathway for the wetlands and the wetland complexes in this interfluve over time scale of 10 102 years we suggest that the evolution of the wetlands in a dynamic fluvial system such as the interfluve region of the egp is governed by two different processes firstly fluvial scouring and channel abandonment provide negative relief at a regional scale and secondly erosional processes cut and fill acting on the local scale transform the narrow and deep fluvial scours into large and shallow wetland systems

a sequence of partial melting reactions at mt stafford central australia metasedimentary gneisses show a rapid change in grade in a 10 km wide low p high t regional aureole at mt stafford in the arunta block central australia migmatite occurs in all but the lowermost of five metamorphic zones which grade from greenschist zone 1 through amphibolite zones 2 3 to granulite facies zones 4 5 the sequence of partial melting reactions inferred for metapelitic rocks is dependant upon protolith temperature and fluid conditions the metapelite solidus in zone 2 reflects vapour present melting at p 3 kbar and t 640 c melting having initially been controlled by the congruent breakdown of the assemblage crd kfs bt qtz at slightly higher temperature andalusite in leucosome formed via the reaction kfs qtz bt h2oand melt and melt having been stabilized by the presence of boron sillimanite coaxially replaces andalusite in the high grade portion of zone 2 in zone 3 large aluminosilicate aggregates in leucosome are armoured by spl crd grt symplectites garnet partially pseudomorphs biotite cordierite or spinel in high grade portions of zone 3 zone 4 grt crd opx bearing metapsammite assemblages and garnet bearing leucosome reflect t 800 c and p 2 2 0 9 kbar in the model kfmash system the principal vapour absent melting step reflected significant modal changes related to the breakdown of the as bt tie line and the establishment of the spl crd tie line the bulk rock geochemistry of migmatite samples straddle the spl crd tie line the aluminous bulk rock composition of the common bedded migmatite restricted its potential to witness garnet forming and orthopyroxene forming reactions minor textural and modal changes in and above zone 3 reflecting biotite destablization in biotite poor assemblages

stratigraphic timing constraints in the davenport province central australia a basis for palaeoproterozoic correlations abstract detailed u pb isotopic dates for intercalated volcanics magmatic intrusions and detrital zircons in clastic sediments constrain the stratigraphic development of the davenport province in central australia to the period ca 1860 1800 ma three basin phases were deposited the warramunga formation unconformably overlain by the ooradidgee group of siliciclastic sedimentary rocks and bimodal volcanics after ca 1840 ma followed by the ca 1820 1800 ma hatches creek group of bimodal volcanism and accompanying siliciclastic sedimentation mafic and felsic intrusions emplaced in lower parts of the stratigraphy are probable subvolcanic feeders to bimodal volcanism in the overlying sequence detrital zircon age spectra are dominated by ca 1880 1840 ma detritus with a subordinate presence of older proterozoic and late archaean components the younger hatches creek group is distinguished by the sparse presence of juvenile 1820 1800 ma detritus which is the same age as contemporaneous volcanism a similar evolution of both stratigraphic ages and zircon provenance is widespread in the lander and ongeva packages of the arunta region where units are now deformed and metamorphosed by later tectonic events and also in the tanami region killi killi formation and ware group basin phases several hundred kilometres to the west

terex toolbox for semi automated selection of fluvial terrace and floodplain features from lidar terraces and floodplains are important indicators of near channel sediment dynamics serving as potential sediment sources and sinks increasing availability of high resolution topography data over large areas calls for development of semi automated techniques for identification and measurement of these features in this study we introduce a novel tool that accommodates user defined parameters including a local relief threshold selected by a variable size moving window minimum area threshold and maximum distance from the channel to identify and map discrete terrace and floodplain surfaces each of the parameters can easily be calibrated for a given watershed or reach subsequently the tool automatically measures planform area absolute elevation and height relative to the local river channel for each terrace polygon we validate the tool in two locations where terrace maps were previously developed via manual digitization from lidar and extensive field mapping campaigns the tool is also tested on six different types of rivers to provide examples of starting selection parameters and to test effectiveness of the tool across a wide range of landscapes generally the tool provides a high quality draft map of terrace and floodplain surfaces across the wide range of environmental conditions for which it has been tested we find that the tool functions best in catchments where the terraces are spatially extensive with distinct differences between the terrace and floodplain the most challenging environments for semi automated terrace and floodplain mapping include steep catchments with dense riparian vegetation and very small terraces 10 m2 in areal extent we then apply the tool to map terraces and floodplains in the root river watershed southeastern minnesota and generate exceedance plots for terrace heights these plots provide a first pass analysis to indicate the tributaries and reaches of the river where terraces constitute a significant source of sediment copyright 2013 john wiley sons ltd

the proterozoic davenport province central australia regional geology and geochronology abstract the davenport province forms the southern part of the tennant creek inlier and lies to the north of the arunta inlier the oldest rocks exposed are turbidites and minor 1880 1870 ma old felsic volcanics of the warramunga group these were folded probably during the barramundi orogeny and intruded by granite before being overlain by the hatches creek group a sequence up to 10 000 m or more thick of fluvial to shallow marine sedimentary and bimodal volcanic rocks a rift sag model of basin development involving crustal extension in an intracratonic setting is suggested for this group interpretation of u pb zircon data for felsic volcanics in the lower part of the hatches creek group is hampered by problems of ancient pb inheritance but a preferred crystallization age of 1820 1810 ma is indicated two episodes of upright concentric folding about nw se and ne sw trending axes preceded emplacement of granite at 1660 ma or earlier rb sr whole rock data for felsic volcanics from the hatches creek group are tentatively interpreted to indicate a region wide hydrothermal alteration event at 1645 44 ma this alteration may have been associated locally with w cu bi and mo mineralization

early proterozoic stream deposits braided or meandering evidence from central australia abstract it has been suggested that meandering stream deposits should be rare in proterozoic rocks this question was addressed during study of the early proterozoic hatches creek group in central australia as the lower part of the group includes up to 4000 m of fluvial sediments most of the 3000 m thick kurinelli sandstone appears to result from braided streams but there is evidence for the existence of meandering stream deposits in the overlying taragan sandstone and in sediments within the treasure volcanics the basal taragan sandstone consists of a fining up cycle in part of which lateral accretion surfaces are present a 28 m thick sedimentary member in the treasure volcanics contains preserved bedforms form sets which provide indirect evidence for the existence of meandering streams the bedforms including dunes 0 1 1 m high are preserved beneath a mudstone layer as a result of a very sudden drop in current velocity during deposition the observed structures can be explained by neck cut off in a meandering stream although the damming or diversion of a stream by lava flows cannot be discounted the hatches creek group thus contains evidence consistent with the existence of meandering stream deposits at two stratigraphic levels meandering streams should form when suitable combinations of bed and suspended load material are available for transport and discharge and slope parameters are within certain limits evidently the lack of land vegetation has not totally precluded the development of meandering streams in the proterozoic

depositional ages of the stratiform base metal deposits at mount isa and mcarthur river australia based on u pb zircon dating of concordant tuff horizons potassium rich tuff beds occur interbedded with major stratiform pb zn mineralization in shales and dolomitic shales of the mount isa group northwest queensland and the mcarthur group northern territory these deposits are some 600 km apart yet they exhibit many similarities which together with regional correlations suggest that the deposits formed by similar processes and that the successions developed more or less contemporaneously zircon is sparsely distributed as tiny crystal fragments or phenocrysts in the tuffs and its morphology and u pb systematics affirm that it is primarily of igneous origin u pb zircon data from a tuff in the mineralized h y c pyritic shale member of the mcarthur group give an age of the tuff of 1 690 super 29 sub 25 m y and from a tuff in the mineralized urquhart shale of the mount isa group an age of 1 670 super 20 sub 17 m y these results are consistent with all other geologic controls and are regarded as the best estimates of the depositional ages of the groups the ages of the mount isa and mcarthur groups are thus the same to within the present experimental uncertainties essentially confirming geologic synchrony of these important sedimentary successions pooled whole rock data from several of the mount isa tuff marker beds give an updated rb sr age of about 1 480 m y interpreted as indicating that isotopic exchange and regional metamorphism had essentially ceased by this time

net local removal of floodplain sediment by river meander migration abstract erosion from the banks of meandering rivers causes a local influx of sediment to the river channel most of the eroded volume is usually replaced in nearby point bars however the typical geometry of river bends precludes the local replacement of all eroded material because i point bars tend to be built to a lower elevation than cutbanks and ii point bars tend to be shorter than the eroding portion of cutbanks because of channel curvature in a floodplain that is in equilibrium i e neither increasing nor decreasing in volume sediment eroded from cut banks must be replaced elsewhere on the floodplain the local imbalance caused by differences in bank height should be balanced primarily by overbank deposition while the local imbalance caused by curvature should be balanced primarily by deposition in abandoned stream courses or oxbow lakes estimates of these local imbalances based on remotely sensed measurements of bank geometry and channel migration have been made on four systems in the united states a 91 km reach of the pearl river in louisiana and mississippi a 62 km reach of the bogue chitto river in louisiana a 35 km reach of the neuse river in north carolina and a 2 7 km reach of the vermillion river in minnesota for these systems the total local imbalance integrated over many bends ranged from 0 36 to 2 27 m 3 yr m of valley length 0 15 to 1 32 m 3 yr m of channel length or 7 to 45 of gross cutbank erosion with a typical value of about 17 when compared with gauged suspended sediment data the measurements provide estimates of the relative importance of floodplains for storing material transported by a river system the data suggest that even if the studied systems are near long term mass balance equilibrium as opposed to undergoing net deposition or erosion almost all of the sand and in some cases much of the silt and clay in transit through these systems is likely to have spent some time stored in an upstream floodplain

overbank sediment deposition patterns for straight and meandering flume channels experiments with the 10 m flood channel facility at hr wallingford uk indicate a fundamental dependency of the overbank deposition pattern of channel suspended sediments on channel planform two experiments 100 and 140 l s 1 in a 1 95 m wide straight channel showed deposition concentrated in a berm along the channel bank little sediment was transferred further onto the floodplain for the larger flow the berm formed further from the channel a single experiment 103 l s 1 with a 1 31 m wide meandering channel showed deposition across the entire floodplain tongue between successive meanders maximum deposition occurred on the downstream side of the meander just past the bend apex these generalized flume results complement the real world but site specific data of field studies copyright 2002 john wiley sons ltd

controls on the occurrence and prevalence of floodplain channels in meandering rivers the process of channelization on river floodplains plays an essential role in regulating river sinuosity and creating river avulsions most channelization occurs within the channel belt e g chute channels but growing evidence suggests some channels originate outside of the channel belt in the floodplain to understand the occurrence and prevalence of these floodplain channels we mapped 3064 km2 of floodplain in indiana usa using 1 5 m resolution digital elevation models dems derived from airborne light detection and ranging lidar data we find the following range of channelization types on floodplains in indiana 6 8 of floodplain area has no evidence of channelization 55 9 of floodplains show evidence e g oxbow lakes of chute channel activity in the channel belt and 37 3 of floodplains contain floodplain channels that form long coherent down valley pathways with bifurcations and confluences and they are active only during overbank discharge whereas the first two types of floodplains are relatively well studied only a few studies have recognized the existence of floodplain channels to understand why floodplain channels occur we compared the presence of channelization types with measured floodplain width floodplain slope river width river meander rate sinuosity flooding frequency soil composition and land cover results show floodplain channels occur when the fluvial systems are characterized by large floodplain to river widths relatively higher meandering rates and are dominantly used for agriculture more detailed reach scale mapping reveals that up to 75 of channel reaches within floodplain channels are likely paleo meander cutoffs the meander cutoffs are connected by secondary channels to form floodplain channels we suggest that secondary channels within floodplains form by differential erosion across the floodplain linking together pre existing topographic lows such as meander cutoffs copyright 2016 john wiley sons ltd

hydrogeomorphological differentiation between floodplains and terraces floodplains and terraces in river valleys play important roles in the transport dynamics of water and sediment while flat areas in river valleys can be identified from lidar data directly characterizing them as either floodplain or terraces isnot yet possible to address this challenge we hypothesize that since geomorphic features are strongly coupled to hydrologic and hydraulic dynamics and their associated variability there exists a return frequency or possibly a narrow band of return frequencies of flow that are associated with floodplain formation and this association can provide a distinctive signature for distinguishing them from terraces based on this hypothesis we develop a novel approach for distinguishing between floodplains and terraces that involves transforming the transverse cross sectional geometry of a river valley into a curve named river valley hypsometric rvh curve and linking hydraulic inundation frequency with the features of this curve our approach establishes that the demarcation between floodplains and terraces can be established from the structure of steps and risers in the rvh curves which can be obtained from the dem data further it shows that these transitions may themselves be shaped by floods with 10 to 100 yr recurrence we additionally show that when floodplain width and height above channel bottom are normalized by bankfull width and depth the ratio lies in a narrow range independent of the scale of the river valley

timing of palaeoproterozoic au cu bi and w mineralization in the tennant creek region northern australia improved constraints via intercalibration of 40ar 39ar and u pb ages abstract the magnitude of systematic uncertainties inherent in comparisons of proterozoic 40ar 39ar and u pb based ages is illustrated via a consideration of age constraints on two contrasting styles of palaeoproterozoic mineralization in northern australia published 40ar 39ar ages for au cu bi mineralization in the tennant creek region range from 1825 to 1829 ma apparently younger than the timing of deformation bracketed by 207pb 206pb zircon ages of igneous rocks at 1850 ma despite this apparent age offset propagation of systematic uncertainties in the 40ar 39ar ages shows that they are indistinguishable from the 1850 ma zircon ages recalculation using revised estimates of the 40k decay constant and age of the 40ar 39ar standard shifts the 40ar 39ar ages to 1847 1851 ma in excellent agreement with 207pb 206pb zircon ages from tennant supersuite igneous rocks and with local geological constraints to the south of tennant creek in the davenport ranges numerous small w prospects have been interpreted to be coeval with post tectonic granites of the devils suite at 1710 1720 ma new 40ar 39ar ages from muscovite selvages on wolframite bearing veins range from 1697 to 1703 ma these ages shift to 1711 to 1717 ma when recalculated using revised estimates for 40k decay constant and age of standard material bringing them into agreement with existing 207pb 206pb zircon ages for devils suite granitoids and consistent with field and geochemical interpretations these examples highlight the importance of considering systematic sources of uncertainty when comparing radiometric ages determined via different isotopic methods particularly in the proterozoic and archean parts of the timescale ongoing work to calibrate the 40ar 39ar and u pb based timescales will further enhance the application of multiple isotopic methods to constrain geological processes

a new longitudinal approach to assess hydrologic connectivity embanked floodplain inundation along the lower mississippi river hydrologic connectivity is fundamental to understanding floodplain processes along meandering river corridors this study contributes to understanding hydrologic connectivity by utilizing a high resolution light detection and ranging dem with a new gis based approach for identifying the precise elevation of flood stage the method created a high resolution longitudinal channel bank profile enabling a detailed examination of embanked floodplain hydrologic connectivity a simple channel cross section approach is likely to result in a large underestimation of floodplain inundation and hydrologic connectivity along meandering river floodplains because of differences in the elevation of the natural levee surface relative to floodplain bottoms and the considerable variability in the elevation of the channel bank profile there is a large disparity in discharge duration associated with floodplain inundation in comparison to river channel bank inundation a discharge duration of 10 is associated with inundation of 87 of the floodplain surface whereas only 53 of the channel bank profile is overtopped an apparent threshold in inundation occurs as the discharge duration decreases below about 35 while a duration of 25 results in very little of the channel bank being overtopped it inundates 50 of the floodplain surface floodplain borrow pits which are created in association with dike construction represent a constant anthropogenic influence on the lower mississippi embanked floodplain morphology and are inundated by low discharge magnitudes the results of the investigation shed new light on the topic of hydrologic connectivity for an important embanked fluvial system that has previously received little attention concerning its physical floodplain processes copyright 2013 john wiley sons ltd

floodplains of large rivers weathering reactors or simple silos abstract large river sediments are mostly derived from tectonically active mountain belts but then undergo a series of sedimentation temporary storage and reworking episodes on their journey to the ocean the long transfer time of these sediments through active floodplains might result in a significant chemical maturation via weathering reactions which is of critical importance for biogeochemical cycles at the earth surface this study reports the chemical composition of river sediments from different locations throughout the courses of the main tributaries of the amazon basin sampling along river depth profiles yields access to the whole grain size and chemical composition range of river sediment here weathering intensities i e losses of na k mg and ca associated with chemical weathering in floodplains are 1 examined as a function of grain size and 2 integrated over the whole grain size range for three selected long river reaches flowing through the foreland and the lowland of the amazon basin the upper maranon the beni and the lower madeira rivers a relatively small na loss through plagioclase dissolution is observed in the madeira reach while an important ca loss due to carbonate dissolution occurs in the two foreland reaches maranon and beni no significant loss of k and mg is observed in any of the reaches showing the low alterability of primary k and mg bearing minerals and suggesting retention of k and mg in the particulate phase by secondary minerals the combination of these findings with previously reported data on the downstream change of dissolved na k mg and ca fluxes suggests that chemical weathering of stable alluvial deposits could also significantly contribute to theweathering flux generated in foreland and lowland areas the comparison between the three amazon reaches and the gangetic plain tends to show that the features observed in the amazon are valid on a global scale finally we show that although resulting in a relatively small change in the chemical composition of the river sediment silicate weathering in the lower madeira floodplain can lead to a co2 drawdown equivalent to ca 10 of the total co2 consumption flux of the whole madeira basin

high resolution basin extent observations and implications for understanding river form and process fifty years of fluvial studies have posited a variety of conceptual frameworks for characterizing river forms and processes throughout entire basins including hydraulic geometry the river continuum concept self organized criticality and sediment links this article uses basin extent high resolution observations of fluvial forms in the nueces river basin texas and yellowstone national park to evaluate the ability of these frameworks to characterize system behavior across a multitude of scales the nueces data were collected with remote sensing methods and the yellowstone data were collected through extensive field surveys the data resolution spatial extent and quality of these data sets allow direct comparison between the two areas the hyperscale comparison supports using of each these frameworks at specific scales but also indicates an irreducible amount of variation in both datasets across many different scales that is not captured by the conceptual frameworks moreover the scales and locations where one framework such as hydraulic geometry works well are often not the same scales and locations where another framework such as the river continuum concept works well because the conceptual frameworks appear to operate at scales and locations distinct from one another the measurement approaches necessary to observe them must also be at different scales and locations for example seeing self organized criticality in a river system is difficult without an extensive survey through space whereas the recognition of sediment links requires quite intense sampling in specific river regions we suggest that these separations between measurement scales represent an incommensurability issue in river studies making it very difficult to both communicate among and test between two or more competing theories making simultaneous hyperscale observations of the river is one approach to minimizing the theory ladeness of observation as deviations from different predictions can be plotted at every scale copyright 2010 john wiley sons ltd

inversion of geological knowledge for fold geometry abstract the process of building three dimensional 3d geological models can be framed as an inverse problem where a model describing the 3d distribution of rock units is non uniquely derived from geological observations the inverse problem theory provides a powerful framework for inferring these parameters from all geological observations in a similar way to how a geologist can iteratively update their structural interpretation while mapping existing geological knowledge is usually indirectly incorporated into 3d models using the geologist s non unique interpretation as form lines cross sections and level maps these approaches treat constraints derived from geological knowledge in the same way as direct observations diluting and confusing both information provided by geological knowledge and hard data resulting in significant subjectivity we present a geological inversion using bayesian inference where geological knowledge can be incorporated directly into the interpolation scheme with likelihood functions and informative prior distributions we demonstrate these approaches on a series of synthetic fold shapes as a proof of concept and a case study from the proterozoic davenport province in the northern territory australia the combined inversion of geological data and knowledge significantly reduces the uncertainty in possible fold geometries where data is sparse or highly ambiguous this could be used by geologists while mapping to propagate information about uncertainties throughout the mapping model building process and would allow for different structural interpretations to be rapidly tested for targeted data collection

tectonic evolution of the pine creek inlier northern territory the pine creek inlier c 66 000 km2 contains early proterozoic sediments and volcanics deposited 1900 ma ago in a basin formed by crustal extension of c 2500 ma granitic basement about 10 km of supracrustals accumulated in 20 ma in shallow marine to continental environments during sagging related to post extensional subsidence deposition in this pine creek geosyncline was succeeded by an orogenic period lasting for 180 ma 1870 1690 ma the top end orogeny felsic and mafic intrusives were emplaced before and after the main deformation which ranged in style from open to tight upright folds in low grade areas in the centre of the region to reclined multiple isoclinal folds in areas of medium to high grade metamorphism in the northeast and west during late orogenesis rift related felsic volcanics and continental sediments were deposited on the metamorphosed sequence to form the katherine volcanic sequence representing a second period of crustal extension the lower part of this sequence was itself mildly deformed by the last significant perturbation of the top end orogeny the hiatus between these early proterozoic events and middle proterozoic deposition is marked by a saprolitic weathered profile indicating a stable subaerial period perhaps as long as 150 ma the cover rocks are the basal part of the mcarthur basin sequence which extends eastward into queensland in the pine creek region they are plateau forming sandstone generally 600 m thick thickening to 2000 m in basins near katherine formed by further movement of the late early proterozoic rift systems the region has remained stable since proterozoic time with only minor reactivation of rift structures to allow accumulation of locally thicker mesozoic and eocene sequences and intrusion of minor mafic to intermediate dykes in the late proterozoic and palaeozoic later eustatic movement led to incursion of shallow palaeozoic and mesozoic seas

geochronology of early to middle proterozoic fold belts in northern australia a review abstract this geochronological review integrates geologically relevant isotopic data from the several early to middle proterozoic fold belts of northern australia a number of firm chronological benchmarks largely established by means of u pb zircon studies now provide a time framework within which to better quantify the tectonostratigraphic history of many of these terranes the apparent worldwide dearth of crustal events in the earliest proterozoic between 2500 and 2000 ma was broken in northern australia with the advent of a major crust forming episode between 1880 and 1850 ma ago these rocks may have evolved from an initial mantle or lower crustal melting and fractionation process about 400 300 ma earlier that is evidenced from sm nd model ages the extent involvement and or degree of assimilation of any pre existing archaean crust is small but whether or not it is negligible or zero is not satisfactorily known the 1880 1850 ma event the barramundi orogeny is well represented in northern australia both lithologically and analytically and the rocks that pre and post date it have a similar tectonic setting over very wide areas of the continent two consistent and widespread elements of this tectonism are regional metamorphism and deformation of the first cycle of supracrustals barramundi orogeny and crystallization of i type k rich felsic magmas closely following and in some cases overlapping with deformational processes in the halls creek inlier the ages of this rapid deep crustal to supracrustal tectonic transition cannot be distinguished within the range 1860 1850 ma this major yet short lived tectonism is mirrored in other fold belts such as pine creek tennant creek and mount isa in which u pb zircon ages give slightly older constraints of 1885 1870 ma 1920 1870 ma and 1885 10 ma respectively the ensuing felsic magmatism in these latter terranes continued for a few tens of millions of years with the crystallization and emplacement of comagmatic volcanic plutonic pairs throughout in the interval 1870 1860 ma in the georgetown and arunta inliers direct evidence of this otherwise ubiquitous event if present is masked by younger high grade metamorphism in the latter however metamorphic crustal components having approximate protolith ages of this order can be inferred from their evolved isotopic signatures the geochronological and geochemical coherency of the extensive early proterozoic 1870 ma magmatism contrasts with that of post 1800 ma magmatism which is less extensive generally anorogenic commonly bimodal in character and varies in age from one terrane to another several major sedimentary basins were being filled at this time major igneous events at 1790 1740 ma 1670 ma and 1500 ma are recognized elongate sublinear volcanic and plutonic belts 1790 1740 ma old are present at mount isa in high grade granitic gneisses of the arunta inlier a few u pb zircon ages and extrapolated rb sr protolith ages are coincident at about 1760 1750 ma indicating that this event may be important in the development of the division 2 sequences of that fold belt the platformal hart dolerite and oenpelli dolerite two of the largest mafic intrusions in the world were emplaced at 1762 25 ma and 1688 13 ma younger felsic plutonism and volcanism gave rise to rapakivi type granites in the mount isa tennant creek and the granites tanami inliers at 1670 ma a time close to that of the aileron deformational metamorphic event in central australia further at 1650 ma there is growing evidence of an unexpectedly coherent hydrothermal episode that reset or disturbed many rb sr ages gave rise to pegmatites and was possibly associated with mineralization in the davenport and eastern arunta inliers discrete middle proterozoic deformational events between 1610 and 1470 ma punctuate the tectonostratigraphic history in the arunta mount isa and georgetown fold belts where they are best documented

an automated method to extract fluvial terraces from digital elevation models the vesdre valley a case study in eastern belgium abstract fluvial terraces are a powerful tool for unraveling the combined tectonic and climatic conditions that controlled directly or indirectly the quaternary incision of rivers terrace long profiles are usually retrieved from sparse traces of ancient floodplains preserved in the present topography however when these traces classically collected from topographic maps aerial photographs and field analyses are too few the inferred profiles may be questionable yet the now available high quality and high resolution digital elevation models dems offer an opportunity to increase greatly the quantity of information usable to reconstruct terrace profiles therefore the purpose of this study was to develop a new dem based method of terrace recognition in order to create a larger database and better constrain the profile reconstruction moreover particular procedures of image and numerical processing were defined to fully automate the analysis basically our method relies on the production of bivariate scatter plots depicting the relation between slope and relative altitude i e the altitude above the current alluvial plain for all pixels of successive sections of the valley for each scatter plot the curve of the lowest slope values observed at every relative altitude is smoothed and its minima are assumed to locate the altitudes of the terrace elements preserved in the section we successfully tested this method in the vesdre valley incised in the ne ardenne massif e belgium notably identifying fault deformation of the profiles the main advantages of our approach are its objectivity exhaustiveness and rapidity allowing fast and coherent analysis of many rivers over extended regions

proterozoic granulite facies metamorphism in the southeastern reynolds range central australia geological context p t path and overprinting relationships in the southeastern reynolds range central australia a low p granulite facies metamorphism affected two sedimentary sequences the lander rock beds and the reynolds range group in the context of the whole of the reynolds range and the adjacent anmatjira range this metamorphism is m3 in a sequence m1 4 that occurred over a period of 250 ma in particular m1 affected the lander rock beds prior to the deposition of the reynolds group m3 has an areally restricted high grade area in the southeastern reynolds range affecting both the reynolds range group and the underlying lander rock beds the effects of m3 are characterized by spinel quartz bearing peak metamorphic assemblages in metapelites which imply peak conditions of 750 c and 4 5 1 kbar and involved isobaric cooling or compression with cooling it is concluded that one of a series of thermal perturbations caused by thinning of mantle lithosphere contemporaneous with crustal thickening was responsible for m3 in the southeastern reynolds range evidence of both the unconformity between the two rock groups and previous metamorphism deformation has been completely erased by recrystallization during m3 d3

automated classifications of topography from dems by an unsupervised nested means algorithm and a three part geometric signature abstract an iterative procedure that implements the classification of continuous topography as a problem in digital image processing automatically divides an area into categories of surface form three taxonomic criteria slope gradient local convexity and surface texture are calculated from a square grid digital elevation model dem the sequence of programmed operations combines twofold partitioned maps of the three variables converted to greyscale images using the mean of each variable as the dividing threshold to subdivide increasingly subtle topography grid cells sloping at less than mean gradient of the input dem are classified by designating mean values of successively lower sloping subsets of the study area nested means as taxonomic thresholds thereby increasing the number of output categories from the minimum 8 to 12 or 16 program output is exemplified by 16 topographic types for the world at 1 km spatial resolution srtm30 data the japanese islands at 270 m and part of hokkaido at 55 m because the procedure is unsupervised and reflects frequency distributions of the input variables rather than pre set criteria the resulting classes are undefined and must be calibrated empirically by subsequent analysis maps of the example classifications reflect physiographic regions geological structure and landform as well as slope materials and processes fine textured terrain categories tend to correlate with erosional topography or older surfaces coarse textured classes with areas of little dissection in japan the resulting classes approximate landform types mapped from airphoto analysis while in the americas they create map patterns resembling hammond s terrain types or surface form classes srtm30 output for the united states compares favorably with fenneman s physical divisions experiments are suggested for further developing the method the arc info aml and the map of terrain classes for the world are available as online downloads

shrimp ionprobe dating of short lived proterozoic tectonic cycles in the northern arunta inlier central australia structural and metamorphic evidence from low p high t metamorphic terranes within the northern arunta inlier central australia indicates that two discrete tectonic cycles affected the region each cycle was associated with compressive deformation coincident with peak granulite facies metamorphism and granite intrusion shrimp u th pb analysis of zircons from early syn and late tectonic granitoids allows the age of the two tectonic cycles to be directly measured the age of the first cycle d1 is determined by emplacement of the mount stafford granite dated at or before 1818 15 ma after the first two foliations of the cycle had formed but before the axial plane cleavage associated with later upright folding the regional extent of this tectono magmatic event is confirmed by an emplacement age of 1818 8 ma measured on the large discordant harverson granite 40 km away the second cycle d2 consisted of four distinct deformation stages d2a 2d the ages of which are constrained by 1785 1775 ma old early syn and late tectonic granitoids the warimbi granite emplaced at or before 1785 22 ma and the granitic protolith to the napperby gneiss inferred to be 1780 10 ma pre date or formed during the earliest foliation s2a zircon considered to have grown at peak granulite facies metamorphic conditions during generation of the dominant s2b foliation gives an age of 1774 6 ma in the possum creek charnockite leucogranite in the napperby gneiss which post dates s2b and large scale upright nw se trending f2d folds yields an age of 1775 12 ma and confirms that the entire tectonic cycle d2a 2d formed in a rapid 10 ma period younger zircons which formed at 1659 6 ma in the napperby gneiss cannot be related to any local structural event but are similar in age to a major magmatic metamorphic episode in the southern arunta black and shaw 1992 150 km away they may be the peripheral manifestation of that event further zircon growth at 1600 ma in the napperby gneiss and possum creek charnockite was caused by hydrothermal fluid fluxing associated with post tectonic pegmatite emplacement these dykes were deformed by amphibolite facies retrograde shear zones ion probe dating of zircon stratigraphy from the granitoids has confirmed the discrete successive tectonic cycles identified by earlier structural and metamorphic studies for the northern arunta inlier at least those cycles or orogenies are associated with short lived 10 ma thermal pulses related to granite magmatism not prolonged thermal perturbations spanning 100 ma or more cf dirks and wilson 1990 dirks and hand 1991 such short lived pulses are intimately associated with granite intrusion and may be a general feature of low p high t metamorphism

intensity of in lake processes in floodplain lakes within the bug river zone of fluvial activity the paper presents a new approach to calculating the erosion and deposition values of floodplain lake basins the erosion deposition index edi the edi is a sum of the basin geometry indices bgis which can be calculated for a separate cross section of the lake the distribution of processes within the basin was investigated in two selected floodplain lakes with the use of bgis field research was carried out in the bug river valley from 1 november 2006 to 31 october 2011 the highest erosion was observed in the lakes located close to the parent river deposition processes were observed in lakes with high inflow of groundwater the results showed that edi values of 48 out of the 71 floodplain lakes ranged from 0 2 to 0 2 spatial distribution of erosion and deposition processes within the lake basins resulted from a velocity of water inflowing or flowing through the basin this was observed especially in contrafluent confluent lake inflow of rivers water via upstream crevasse occurred later than via downstream one but energy of flowing water was higher which favoured erosion of this part of the lake basin copyright 2013 john wiley sons ltd

multi scale assessment of overflow driven lateral connectivity in floodplain and backwater channels using lidar imagery overflow driven lateral connectivity significantly influences the spatial distribution and diversity of floodplain habitats and biota proper understanding of lateral connectivity in floodplain and backwater channels is therefore critical for assessment of river quality and for targeting management or restoration actions in this study we present a methodological framework for spatial and temporal assessments of overflow driven lateral connectivity at two spatial scales bypass reach and backwater channel firstly we compute the relative elevations as well as overflow discharge duration and frequency using a simple raster based method that uses a lidar digital elevation model dem rating curves and streamflow time series subsequently we analyse the accuracy of this approach with respect to the accuracy of a dem and evaluate its further applications altogether four 10 km long bypass reaches and 11 backwater channels are analysed located along the rhone river corridor in france the results proved the precision of the method to be affected by the lidar dem accuracy which was on average more precise in a typically homogeneous floodplain setting rather than for backwater channel plugs with pronounced topographic complexity and usually riparian forest canopy amongst the four studied reaches bregnier cordon proved to have the greatest flooding dynamics followed by belley and chautagne the hydrological connectivity pattern of pierre benite differed significantly three longitudinal patterns of hydrological connectivity of backwater channels displayed stepwise advancement of the water the presented results can be used to assess ecological potential of floodplain habitats and their historic and prospective evolution through time copyright 2014 john wiley sons ltd

historical changes in channel network extent and channel planform in an intensively managed landscape natural versus human induced effects abstract humans have become major geomorphological agents effecting substantial change in the characteristics of earth s physical landscapes the agricultural midwest of the united states is a region marked by pronounced human influence at the landscape scale humans undoubtedly have strongly influenced critical zone processes including fluvial processes in intensively managed agricultural landscapes yet the exact nature of human alteration of these processes is unknown this study documents historical changes in the extent of the stream channel network and in channel planform within the upper sangamon river basin an intensively managed agricultural watershed in illinois results indicate that the modern channel network is nearly three times more extensive than the channel network in the 1820s most change in drainage density has occurred in headwater portions of the basin where numerous drainage ditches have been added to the network to drain flat uplands no detectable change in channel position is evident between 1940 and 2012 along about 60 of the total length of the sangamon river and its major tributaries nearly 30 of the total length exhibits change related to meander dynamics cutoffs and lateral migration whereas about 8 has changed as a result of channelization channelized sections typically remain straight for decades following human modification supporting the notion that humans produce long lasting catastrophic change in channel planform in this region the findings confirm that humans are effective agents of morphological change in fluvial systems in this intensively managed watershed documenting human induced versus natural changes in fluvial systems is important for evaluating how other critical zone processes in intensively managed landscapes have been affected by these changes human induced changes in channel extent and planform most likely have altered this landscape from one dominated by biogeochemical transformations and storage of water and sediment prior to agricultural development into one now characterized by enhanced fluxes of water sediment and nutrients

physical basis for quasi universal relationships describing bankfull hydraulic geometry of sand bed rivers empirical data indicate that hydraulic geometry relationships for single thread sand bed rivers i e rivers with median bed material size between 0 062 and 0 50 mm can be delineated such that bankfull width bankfull depth and channel slope are related in consistent ways to bankfull discharge such relationships ought to be the external expression of physical relationships intrinsic to sand bed river dynamics in this study a back calculation is performed to identify parameters exponents and coefficients for three relationships taken to be intrinsic to sand bed rivers 1 a generalized manning strickler resistance relationship 2 a relationship for channel forming shields number and 3 a relationship for sand yield at bankfull flow to back calculate parameters for the physical relationships first the hydraulic geometry relationships are expressed in suitable dimensionless form second the physical relationships are expressed with coefficients and exponents that are analytically related to p

sedimentology stratigraphy and tectonic implications of a paleo proterozoic continental extensional basin the el sherana edith river groups northern territory australia the ca 1 83 ga el sherana edith river basin of northern territory australia contains terrestrial sedimentary and volcanic rocks deposited during continental extension or transtension braid pl

temperature and bulk composition control on the growth of monazite and zircon during low pressure anatexis mount stafford central australia the formation age and trace element composition of zircon and monazite were investigated across the prograde low pressure metamorphic sequence at mount stafford central australia three pairs of inter layered metapelites and metapsammites were sampled in migmatites from amphibolite facies t 600 c to granulite facies conditions t 800 c sensitive high resolution ion microprobe u pb dating on metamorphic zircon rims and on monazite indicates that granulite facies metamorphism occurred between 1795 and 1805ma the intrusion of an associated granite was coeval with metamorphism at 1802 3ma and is unlikely to be the heat source for the prograde metamorphism metamorphic growth of zircon started at t 750 c well above the pelite solidus zircon is more abundant in the metapelites which experienced higher degrees of partial melting compared with the associated metapsammites in contrast monazite growth initiated under sub solidus prograde conditions at granulite facies conditions two distinct metamorphic domains were observed in monazite textural observations petrology and the trace element composition of monazite and garnet provide evidence that the first metamorphic monazite domain grew prior to garnet during prograde conditions and the second in equilibrium with garnet and zircon close to the metamorphic peak ages from sub solidus prograde and peak metamorphic monazite and zircon are not distinguishable within error indicating that heating took place in less than 20 myr

the influence of floodplain geomorphology and hydrologic connectivity on alligator gar atractosteus spatula habitat along the embanked floodplain of the lower mississippi river abstract the floodplain geomorphology of large lowland rivers is intricately related to aquatic ecosystems dependent upon flood pulse dynamics the alligator gar atractosteus spatula is native to the lower mississippi river and dependent upon floodplain backwater areas for spawning in this study we utilize a geospatial approach to develop a habitat suitability index for alligator gar that explicitly considers hydrologic connectivity and the floodplain geomorphology along a frequently inundated segment of the lower mississippi river the data sets include landsat imagery a high resolution lidar digital elevation model dem national hydrography dataset nhd and hydrologic and geomorphic data a habitat suitability index is created based on the extent and frequency of inundation water depth temperature and vegetation a comparison between the remote sensing approach and the nhd revealed substantial differences in the area and location of water bodies available for alligator gar spawning the final habitat suitability index indicates that a modest proportion 19 of the overall embanked floodplain is available for alligator gar spawning opportunities exist for management efforts to utilize engineered and natural geomorphic features to facilitate hydrologic connectivity at flow levels below flood stage that would expand the habitat of alligator gar across the floodplain the study results have direct implications regarding environmental restoration of the lower mississippi an iconic example of an embanked meandering river floodplain

automatic geomorphic feature extraction from lidar in flat and engineered landscapes 1 high resolution topographic data derived from light detection and ranging lidar technology enables detailed geomorphic observations to be made on spatially extensive areas in a way that was previously not possible availability of this data provides new opportunities to study the spatial organization of landscapes and channel network features increase the accuracy of environmental transport models and inform decisions for targeting conservation practices however with the opportunity of increased resolution topographic data come formidable challenges in terms of automatic geomorphic feature extraction analysis and interpretation low relief landscapes are particularly challenging because topographic gradients are low and in many places both the landscape and the channel network have been heavily modified by humans this is especially true for agricultural landscapes which dominate the midwestern united states the goal of this work is to address several issues related to feature extraction in flat lands by using geonet a recently developed method based on nonlinear multiscale filtering and geodesic optimization for automatic extraction of geomorphic features channel heads and channel networks from high resolution topographic data here we test the ability of geonet to extract channel networks in flat and human impacted landscapes using 3 m lidar data for the le sueur river basin a 2880 km 2 subbasin of the minnesota river basin we propose a curvature analysis to differentiate between channels and manmade structures that are not part of the river network such as roads and bridges we document that laplacian curvature more effectively distinguishes channels in flat human impacted landscapes compared with geometric curvature in addition we develop a method for performing automated channel morphometric analysis including extraction of cross sections detection of bank locations and identification of geomorphic bankfull water surface elevation using the slope plotted along each channel floodplain cross section we demonstrate the ability to identify and measure the height of river banks and bluffs finally we present an example that demonstrates how extracting such features automatically is important for modeling channel evolution water and sediment transport and channel floodplain sediment exchange

non linearity of reach hydraulic geometry relations summary reach average hydraulic geometry rhg defines the relations between the average hydraulic variables estimated at river reach water depth velocity channel width and the discharge single log linear models are classically used by fluvial geomorphologists hydrologists and ecologists to represent these relations in this paper we show that these single log linear models are not relevant in most of cases and so can lead to significant errors rhg estimated on 15 alluvial river reaches the catchment sizes vary from 10 km 2 to 1700 km 2 were found non linear for two thirds of the river reaches when considering discharges ranging from low to bankfull flows so we propose using two power functions or log linear to model these relations i e the log piecewise linear model this model can detect a discharge qbreak i e a physical transition or break point between both relations from very low flows about 30 of the median discharge to qbreak a first relation is comparable to the rhg found in the literature for aquatic habitat analysis the second relation is relevant for flows ranging from qbreak to bankfull discharge and therefore may be more useful for sediment transport and flood routing analysis averaging along a reach including several pool riffle units makes it difficult to clearly ascribe the form of rhg to particular physical processes the non linearity of rhg may have multiple origins the presence of lateral gravel bars the hydraulic conditions of riffle cross sections a change in the resistance to flow with water depth vegetation sediment influences further research is needed to focus on the physical processes that govern the rhg non linearity

discrete proterozoic structural terranes associated with low p high t metamorphism anmatjira range arunta inlier central australia tectonic implications structural overprinting relationships indicate that two discrete terranes mt stafford and weldon occur in the anmatjira range northern arunta inlier central australia in the mt stafford terrane early recumbent structures associated with d1a 1b deformation are restricted to areas of granulite facies metamorphism and are overprinted by upright km scale folds f1c which extend into areas of lower metamorphic grade structural relationships are simple in the low grade rocks but complex and variable in higher grade equivalents the three deformation events in the mt stafford terrane constitute the first tectonic cycle d1 d2 deformation in the weldon terrane comprises the second tectonic cycle the earliest foliation s2a was largely obliterated by the dominant reclined to recumbent mylonitic foliation s2b produced during progressive non coaxial deformation with local sheath folds and w to sw directed thrusts locally d2d tectonites have been rotated by n s trending upright f2c folds but the regional upright fold event f2d also evident in the adjacent reynolds range rotated earlier surfaces into shallow plunging nw se trending folds that dominate the regional outcrop pattern the terranes can be separated on structural metamorphic and isotopic criteria a high strain d2 mylonite zone produced during w to sw directed thrusting separates the weldon and mt stafford terranes 1820 ma megacrystic granites in the mt stafford terrane intruded high grade metamorphic rocks that had undergone d1a and d1b deformation but in turn were deformed by s1c which provides a minimum age limit for the first structural metamorphic event 1760 ma charnockites in the weldon terrane were emplaced post d2a and metamorphosed under granulite facies conditions during d2b constraining the second tectonic cycle to this period each terrane is associated with low p high t metamorphism characterized by anticlockwise p t t paths with the thermal peaks occurring before or very early in the tectonic cycle these relations are not compatible with continental style collision nor with extensional tectonics as the deformation was compressional the preferred model involves thickening of previously thinned lithosphere at a stage significantly after 50 ma the early extensional event compression was driven by external forces such as plate convergence but deformation was largely confined to and around composite granitoid sheets in the mid crust the sheets comprise up to 80 of the terranes and induced low p high t metamorphism including migmatization thereby markedly reducing the yield strength and accelerating deformation of the country rocks mid crustal ductile shearing and reclined to recumbent folding resulted followed by upright folding that extended beyond the thermal anomaly thus thermal softening induced by heat focusing is capable of generating discrete structural terranes characterized by subhorizontal ductile shear in the mid crust localized around large granitoid intrusions

tectonic evolution of proterozoic australia proterozoic australia has long been interpreted as a single intact continent in which all tectonic and magmatic activity was intracratonic this paper proposes an alternative hypothesis in which numerous fragments of continental crust were assembled by plate tectonic processes the assembly was completed between 1300 and 1100 ma when the crustal fragments were combined as an early component of the rodinian supercontinent rifting and fragmentation of archaean continents began in the late archaean and continued into the proterozoic passive margin deposits such as those of the hamersley basin accumulated on isolated fragments of archaean crust these numerous fragments were subsequently assembled into three cratons by 1830 ma a west australian craton was established by collision of the archaean pilbara and yilgarn cratons which were joined along the capricorn orogen similarly a south australian craton developed by amalgamation of the proto gawler and proto curnamona cratons along the kimban orogen a north australian craton appears to have formed by accretion of numerous crustal fragments including the kimberley pine creek lucas and altjawarra cratons with sutures marked by the king leopold halls creek tennant creek and proto isan orogens the southern margin of the north australian craton was the site of repeated terrane accretion and orogenic activity between 1880 ma and 1400 ma this included an orogenic event at 1880 1850 ma the strangways 1780 1730 ma argilke 1680 1650 ma and chewings 1620 1580 ma orogenies and the intracratonic anmatjira uplift 1500 1400 ma intracratonic rifting at 1750 to 1710 ma and 1640 to 1600 ma produced the mcarthur basin and related minor basins parts of which were deformed by the isan orogeny at 1600 and 1530 ma rifting along the line of the capricorn orogen led to deposition in the overlying intracratonic bangemall basin between 1630 and 1300 ma along the eastern margin of the south australian craton the 1670 to 1600 ma olarian orogeny marks interaction with now obscured continental crust to the east tectonic activity between 1300 and 1100 ma led to the assembly of proterozoic australia as an early component of the supercontinent of rodinia this first involved the amalgamation of the west australian and north australian cratons followed by collision with the south australian craton the centralian superbasin developed over the junction of the north south and west australian cratons between 830 and 750 ma rifting to the east formed the adelaide geosyncline at 830 ma this was followed by the breakup of rodinia with the rifting apart of laurentia and gondwanaland along the eastern margin of proterozoic australia at 750 ma and the subsequent formation of the palaeo pacific ocean after the breakup of rodinia a series of northeast southwest compressional events followed by periods of relaxation reflect the assembly of a new supercontinent old lines of weakness were reactivated culminating in the intracratonic king leopold paterson petermann ranges and pinjarra orogenies between 620 and 540 ma subsequent reactivation continued into the phanerozoic with the widespread eruption of continental flood basalts and the formation of intracratonic basins 540 530 ma

dynamics of 30 large channel bars in the lower mississippi river in response to river engineering from 1985 to 2015 abstract channel bars are a major depositional feature in alluvial rivers and their morphodynamics has been investigated intensively in the past several decades however relatively less is known about how channel bars in alluvial rivers respond to river engineering and regulations in this study we assessed 30 yr morphologic changes of 30 large emerged bars located in a 223 km reach of the highly regulated lower mississippi river from vicksburg mississippi to the mississippi atchafalaya river diversion landsat imagery and river stage data between 1985 and 2015 were utilized to characterize bar morphologic features and quantify decadal changes based on bar surface areas estimated with the satellite images at different river stages a rating curve was developed for each of the 30 bars to determine their volumes results from this study show that the highly regulated river reach favored the growth of mid channel and attached bars while more than half of the point bars showed degradation currently the mid channel and attached bars accounted for 38 and 34 of the total volume of the 30 bars the average volume of a single mid channel bar is over two times that of an attached bar and over four times that of a point bar overall in the past three decades the total volume of the studied 30 bars increased by 110 118 000 m 3 41 total dike length in a dike field was found mostly contributing to the bar volume increase currently the emerged volume of the 30 bars was estimated approximately 378 183 000 m 3 the total bar volume is equivalent to 530 million metric tons of coarse sand based on an average measured bulk density of 1 4 t m 3 for the bar sediment the findings show that these bars are large sediment reservoirs

u_pb zircon dating of tectonomagmatic events in the northern arunta inlier central australia abstract the mount doreen area of the northern arunta inlier has a proterozoic magmatic and tectonic history that extends over 300 ma the oldest unit the turbiditic lander rock beds lrb was folded and metamorphosed from greenschist to granulite grade during the yuendumu tectonic event a u pb zircon age of 1880 5 ma for the late tectonic ngadarunga granite provides a minimum age for this event and supports its correlation with the widespread barramundi orogeny of northern australia two subsequent major deformations the hardy and the wabudali tectonic phases considered to represent discrete phases of the strangways orogeny are tentatively placed at around 1770 ma the hardy tectonic phase locally retrogressed the lrb and produced strong foliations in some granites including one of the carrington suite dated at 1779 6 ma the wabudali tectonic phase formed high strain zones in places more than 2 km wide within which the sedimentary reynolds range group was tightly folded and the lrb were refolded and retrogressed felsic volcanics and arenites of the fault bound nicker beds and patmungala beds dated at 1772 5 ma and 1799 10 ma respectively were also tightly folded during the strangways orogeny juxtaposition of low grade and high grade lrb took place during faulting that occurred after the 1770 ma tectonism but prior to post tectonic granites which may be indirectly related to the 1600 ma chewings orogeny of the southern arunta inlier one post tectonic granite 1635 9 ma is associated with a mafic to intermediate intrusive complex and another 1567 11 ma is part of an extensive megacrystic suite that intrudes folded reynolds range group zircon inheritance was found in five of the six analysed samples with ages ranging from 1 85 to 3 45 ga

floodplain width adjustments in response to rapid base level fall and knickpoint migration abstract geomorphology has long been engaged in characterizing the form and understanding the evolution of floodplains this study primarily examines floodplain width in four tributaries to the minnesota river in southern minnesota namely the maple le sueur and blue earth rivers and seven mile creek the tributary systems are relatively young having formed after retreat of the wisconsinan ice sheet and are rapidly evolving in response to a base level fall of nearly 70 m 13 400 ybp as a result the lower reaches of all four river channels are aggressively incising this study applies a new freely available open code plug in for arcgis to measure floodplain width as a function of elevation above the geomorphic top of bank systematic changes are observed in all four systems above the steep incising knickzone reaches of each of the tributaries relatively wide and mostly unconfined floodplains are observed within the knickzone floodplains progressively narrow to between 25 60 of their width above the knickzone despite the fact that sediment loads increase significantly in the downstream direction a power law relationship is consistently observed between floodplain width and the ratio of local channel slope to contributing drainage area to about the negative one third power in all four rivers this same power law relationship is observed for two other rivers that differ significantly from our study systems in climatic and tectonic environment as well as base level history

floodplain sedimentation in the upper mississippi valley natural versus human accelerated abstract understanding the time scales and pathways for response and recovery of rivers and floodplains to episodic changes in erosion and sedimentation has been a long standing issue in fluvial geomorphology floodplains are an important component of watershed systems because they affect downstream storage and delivery of overbank flood waters and they also serve as sources and temporary sinks for sediments and toxic substances delivered by river systems here 14c and 137cs isotopic dating methods are used along with ages of culturally related phenomena associated with mining and agriculture to determine rates of sedimentation and morphologic change for a reach of the upper mississippi river and adjacent tributaries in southwestern wisconsin and northwestern illinois the most important environmental change that influenced fluvial activity in this region during last 10 000 years involved the conversion of a late holocene mosaic of prairie and forest to a landscape dominated by cropland and pastureland associated with euro american settlement results presented herein for the upper mississippi valley umv show that the shift from pre agriculture natural land cover to landscape dominance by agricultural land use of the last 175 200 years typically increased rates and magnitudes of floodplain sedimentation by at least an order of magnitude accelerated overbank flooding led to increased bank heights on tributary streams and in turn contributed to more frequent deep flows of high energy these high energy flows subsequently promoted bank erosion and lateral channel migration and the formation of a historical meander belt whose alluvial surface constitutes a new historical floodplain inset against the earlier historical floodplain the new historical floodplain serves as a flume like channel that provides efficient downstream transport of water and sediment associated with moderate and large magnitude floods floodplains on lower tributaries however continue to experience rates of overbank sedimentation that are of anomalously high magnitude given improved land cover and land conservation since about 1950 this lower valley anomaly is explained by minimal development of historical agriculture period meander belts because of relatively low stream power in these channel and floodplain reaches of relatively low gradient in general long term pre agriculture rates of vertical accretion between about 10 000 and 200 years ago averaged about 0 2 mm yr 1 in tributary watersheds smaller than about 700 km2 and about 0 9 mm yr 1 on the floodplain of the upper mississippi river where the contributing watershed area increases to about 170 000 km2 on the other hand rates of historical vertical accretion during the period of agricultural dominance of the last 200 years average between 2 and 20 mm yr 1 with short episodes of even higher rates during times of particularly poor land conservation practices significant hydrologic effects of mining and agricultural started by the 1820s and became widespread in the study region by the mid 19th century the hydrologic and geomorphic influences of mining were relatively minor compared to those related to agriculture high resolution dating of floodplain vertical accretion deposits shows that large floods have frequently provided major increments of sedimentation on floodplains of tributaries and the main valley upper mississippi river the relative importance of large floods as contributors to floodplain vertical accretion is noteworthy because global atmospheric circulation models indicate that the main channel upper mississippi river should experience increased frequencies of extreme hydrologic events including large floods with anticipated continued global warming instrumental and stratigraphic records show that coincident with global warming a shift to more frequent large floods occurred since 1950 on the upper mississippi river and these floods generally contributed high magnitudes of floodplain sedimentation

hydraulic geometry of stream reaches abstract variation in river hydraulic geometry throughout stream networks is central to the problems of catchment management because of its influence on flow and sediment routing physical habitats and channel floodplain interactions in its simplest form at a station hydraulic geometry is described by power functions relating the surface width water depth and mean velocity at a channel cross section to discharge this paper extends hydraulic geometry analysis to represent the mean and variation of hydraulic characteristics along a river reach as power functions of discharge using 54 surveys of 17 river reaches mostly in south east australia it is shown that five reach hydraulic variables are sufficient to characterise the gross hydraulic conditions along a river reach the means and coefficients of variation of surface width and hydraulic depth plus the coefficient of variation of cross sectional velocity exponents for the mean width and mean depth hydraulic geometry relations are sensitive to measurement and cross section location and may best be treated as constant for regional studies coefficients for the mean width and mean depth hydraulic geometry relations are correlated positively with mean discharge and negatively with reach gradient respectively further analysis of variations in reach hydraulic geometry parameters particularly the power function coefficients in relation to river type flow parameters sediment load bank material and bank vegetation is warranted reach hydraulic geometry relations show considerable potential for improving analyses of fluvial processes and physical habitats across catchments

moho geometry along a north south passive seismic transect through central australia abstract receiver functions from a temporary deployment of 25 broadband stations along a north south transect through central australia are used to retrieve crustal and uppermost mantle structural constraints from a combination of different methods using h k stacking as well as receiver function inversion overall thick crust with significant thickness variation along the profile 40 to 55 km is found bulk crustal v p v s values are largely in the felsic to intermediate range with the southernmost stations on the gawler craton exhibiting higher values in excess of 1 8 a common conversion point ccp stacking profile shows three major discontinuities of the crust mantle boundary 1 a two sided moho downwarp beneath the musgrave province which has previously been associated with the neoproterozoic to early cambrian petermann orogeny 2 a moho offset along the redbank shear zone further north attributed to the middle to late paleozoic alice springs orogeny and 3 another moho offset further north located at the boundary between the davenport and warramunga provinces which has not been imaged before in all cases the difference in crustal thickness between the two sides of the offset is 8 10 km unlike the two southern moho offsets the northernmost one does not coincide with a prominent gravity anomaly its location and the absence of known reactivation events in the region make it likely that it belongs to a proterozoic suture zone that marks a previously unknown block boundary within the north australian craton

expert driven semi automated geomorphological mapping for a mountainous area using a laser dtm in this paper a semi automated method is presented to recognize and spatially delineate geomorphological units in mountainous forested ecosystems using statistical information extracted from a 1 m resolution laser digital elevation dataset the method was applied to a mountainous area in austria first slope angle and elevation characteristics were determined for each key geomorphological unit occurring in the study area second a map of slope classes derived from the laser dtm was used in an expert driven multilevel object oriented approach the resulting classes represent units corresponding to landforms and processes commonly recognized in mountain areas fluvial terrace alluvial fan slope with mass movement talus slope rock cliff glacial landform shallow incised channel and deep incised channel the classification result was compared with a validation dataset of geomorphological units derived from an analogue geomorphological map for the above mentioned classes the percentages of correctly classified grid cells are 69 79 50 64 32 61 23 and 70 respectively the lower values of 32 and 23 are mainly related to inaccurate mapping of rock cliffs and shallow incised channels in the analogue geomorphological map the accuracy increased to 76 and 54 respectively if a buffer is applied to these specific units it is concluded that high resolution topographical data derived from laser dtms are useful for the extraction of geomorphological units in mountain areas

spillage sedimentation on large river floodplains active deposition across the floodplains of large rivers arises through a variety of processes collectively these are here termed spillage sedimentation three groups of 11 spillage sedimentation styles are identified and their formative processes described form presences on large river floodplains show different combinations of active spillage styles only some large floodplains have prominent levees some have coarse splays many have accessory channel dispersion and reworking while still water sedimentation in lacustrine environments dominates some lower reaches infills are also commonly funnelled into prior and often linear negative relief forms relating to former migration within the mainstream channel belt 2016 the authors earth surface processes and landforms published by john wiley sons ltd shuttle radar topography mission srtm and landsat 8 data are used to map spillage form types and coverage along a 1700 km reach of the amazon that has an active floodplain width of up to 110 km with a systematic character transformation down valley spillage forms associated directly with mainstream processes rarely account for more than 5 of the floodplain deposits there is a marked decrease in floodplain point bar complexes pbc over 1700 km downstream from 34 to 5 and an increase in the prevalence of large water bodies 2 to 37 and accompanying internal crevasses and deltas 0 to 5 spillage sedimentation is likely within the negative relief associated with these forms depending on mainstream sediment laden floodwater inputs 2016 the authors earth surface processes and landforms published by john wiley sons ltd spillage style dominance depends on the balance between sediment loadings hydrological sequencing and morphological opportunity down river form sequences are likely to follow gradient change prior up river sediment sequestration and the altered nature of spilled loads but also crucially local floodplain relief and incident water levels and velocities at spillage times considering style distribution quantitatively as a spatially distributed set of identifiable forms emphasizes the global variety to spillage phenomena along and between large rivers 2016 the authors earth surface processes and landforms published by john wiley sons ltd

petrographic composition of polish lignite and its possible use in a fluidized bed gasification process abstract the main objectives of the study include the estimation of the proportion of lithotypes and macerals in lignite deposits and the determination of petrographic criteria for the assessment of quality and possible use of lignite in fluidized bed gasification process measures taken to meet the objectives included field research and laboratory studies the study included results from 293 samples of low rank coal from polish deposits the data used in the study included currently exploited abandoned and prospective lignite deposits lignite deposits were divided into seven regions a western b legnica c wielkopolska d konin e od belchatow f north and g radom polish lignite deposits include mainly humic coal with four basic lithotypes identified xylitic coal xylo detritic coal detro xylitic coal and detritic coal dominating lithotypes include detritic coal and xylo detritic coal fibrous xylites present only in minor amounts in polish lignite have a negative influence on coal gasification process grinding the highest content of fibrous xylites is observed in the konin region petrographic composition of coal was determined on the basis of maceral group and the sum of gelified macerals it has been found that the influence of macerals from the huminite group on fluidized bed gasification is significant the average content of this component in tested coal is 89 meanwhile average content of macerals from the liptinite group in polish coal is 8 while for macerals from the inertinite group it is 3 the content of mineral matter in lignite deposits is a highly variable parameter according to the proposed scheme in order to be suitable for fluidized bed gasification the maceral composition of the coal should contain at least 80 huminite while the sum of the macerals from the inertinite group and mineral matter should be less than 20 taking into account the whole region it should be noted that petrographic composition of lignite in almost all of the deposits allows its use in the process of fluidized bed gasification however limited usefulness in this process can be observed in some of the deposits containing bituminiferous lignite

natural streams and the legacy of water powered mills gravel bedded streams are thought to have a characteristic meandering form bordered by a self formed fine grained floodplain this ideal guides a multibillion dollar stream restoration industry we have mapped and dated many of the deposits along mid atlantic streams that formed the basis for this widely accepted model these data as well as historical maps and records show instead that before european settlement the streams were small anabranching channels within extensive vegetated wetlands that accumulated little sediment but stored substantial organic carbon subsequently 1 to 5 meters of slackwater sedimentation behind tens of thousands of 17th to 19th century milldams buried the presettlement wetlands with fine sediment these findings show that most floodplains along mid atlantic streams are actually fill terraces and historically incised channels are not natural archetypes for meandering streams

the possibility of underground gasification of lignite from polish deposits abstract the paper focuses on the possibility of underground gasification of lignite from polish deposits lignite deposits in poland are part of the european lignite formation the profile of coal bearing sediments in poland is several hundred meters paleocene pliocene but it is fragmented vertically and is not complete at any point it includes marine and brackish sediments as well as paleogene and neogene land sediments lignite deposits originated both in platform areas and sedimentary basins in orogenic belts the coals form extensive seams or lenses ranging from few meters to several dozen meters in thickness there are 90 documented lignite deposits in poland currently geological resources of lignite are about 26 132 mt on the polish lowland ten lignite eight major and two accompanying seams have been distinguished within the paleogene and neogene stratigraphic columns only three of them 1st mid polish 2nd lusatia 3rd cinawa and locally five additionally 2nda lubin and 4th d browa are important from the economic point of view the annual production of lignite in polish open cast mines amounts to 65 0 mt per year while it is primarily used by power plants however chemical processing of lignite is not yet developed it is planned that pilot plants are to be developedfor underground lignite gasification in the near future the geological structure of the tertiary coal bearing formation in the polish lowland was the basis for the development of guidelines and parameters for criteria verification of resource base ortho lignite for underground coal gasification ucg in poland lignites from the polish coal deposits havethe characteristics of low rank coal mean rr 0 2 0 35 an average carbon content at around 62 65 c high moisture content 50 and net calorific value ncv 6 20 mj kg mean 8 0 mj kg petrographic composition of lignite 80 humic components makes it a preferred material for chemical processing the available resources and lignite deposits have been verified on the basis of the assumed geological and technological criteria since the geologic and reservoir conditions are accompanied by the requirements of environmental protection protection of groundwater reservoirs of drinking water and distance requirements between the gasification plants and residential buildings roads and transmission lines a significant reduction in coal resources suitable for underground gasification in poland occurred the aforementioned criteria were applied to the initial verification of lignite resources in the polish deposits the deposits useful for underground gasification are mainly located in the area from glogow up to ciniawa and legnica some individual deposits are scattered in different locations e g weglewice residual part of the turow deposit

channel planform geometry and slopes from freely available high spatial resolution imagery and dem fusion implications for channel width scalings erosion proxies and fluvial signatures in tectonically active landscapes article i nfo the rapid expansion of high spatial resolution optical sensors and imagery over the last decade presents ex ceptional opportunities for quantifying visible attributes of geomorphic systems in this study we detail a simple robust methodology changeom to extract continuous channel width and centerline datasets for single thread channels using freely available high spatial resolution imagery currently available in google earth and bing maps comparisons with a global dataset of field and lidar derived channel widths indicate minimal errors associated with the imagery and changeom methodology b1 overall while examples from the goriganga river indian himalaya and the yakima river wa usa emphasize the benefit of em pirical width values over established channel width scalings in deciphering fluvial responses to complex landscape forcings in tectonically active regions additionally accurate centerline delineation from the changeom methodology provides improved sinuosity measurements and when fused with coarse resolution digital elevation models dems removes along profile shortening and coincident increases in reach scale channel slope lastly comparisons of aster gdem v2 srtm v4 1 and lidar channel profiles extracted in moderate to high relief regions demonstrate the inferiority of the aster gdem for channel slope calcula tions despite the apparent spatial resolution advantages 9 the methodology presented here will facili tate new discoveries in the fluvial environment that have historically been difficult due to access and imagery resolution issues and provide greater perspective on channel signatures and responses to a host of landscape forcings especially in tectonically active bedrock and lower order drainage systems

strong tectonic and weak climatic control of long term chemical weathering rates the relationships among climate physical erosion and chemical weathering have remained uncertain because long term chemical weathering rates have been difficult to measure here we show that long term chemical weathering rates can be measured by combining physical erosion rates inferred from cosmogenic nuclides with dissolution losses inferred from the rock to soil enrichment of insoluble elements we used this method to measure chemical weathering rates across 22 mountainous granitic catchments that span a wide range of erosion rates and climates chemical weathering rates correlate strongly with physical erosion rates but only weakly with climate implying that by regulating erosion rates tectonic uplift may significantly accelerate chemical weathering rates in granitic landscapes

quantitative resolution of the debate over antiquity of the central australian landscape implications for the tectonic and geomorphic stability of cratonic interiors we report the first measure of long 100 myr and short 1 myr term denudation rates from key geologically stable landforms in the davenport range central australia these landforms have previously been assigned a cambrian age which arguably places them amongst the oldest persistent landforms on the continent if not on earth our results from combined apatite fission track thermochronology and in situ cosmogenic radionuclide analyses using 10 be and 26 al show that while average exhumation rates are low the denudation history for this cratonic region is incompatible with extreme sub aerial longevity and long term tectonic and geomorphic stability our revised model for the landscape evolution of this region is consistent with one of maximum burial prior to and during the mesozoic followed by a phase of kilometre scale exhumation that was largely complete by the beginning of the cainozoic we suggest that a similar process of burial and exhumation has probably been responsible for the sub aerial preservation of seemingly ancient landforms elsewhere in australia

late holocene alluvial history of the cuyama river california usa dryland river deposits are archives of past changes in fluvial system form and process chronostratigraphic reconstruction of the late holocene alluvial history of the cuyama river in west central california reveals past spatial and temporal variation in dryland channel form and process the modern cuyama river consists of a wide braided reach in the upper drainage basin a narrower arroyo reach in the middle of the drainage basin and a bedrock canyon reach in the lower drainage basin that drains to the santa maria coastal plain along the arroyo reach late holocene stratigraphy is well exposed and is the focus of this study between ca 1700 and 350 yr b p two widespread deposits of tabular bedded clay silt and fine sand were deposited separated by a buried soil formed between 950 and 700 yr b p channel incision occurred between 550 and 350 yr b p next deposition of massive to bedded sands occurred in a pattern alternating between poorly confined deposition on top of older deposits onto the broad valley floor and channelized deposition along the valley axis inset into older deposits the superposed deposits now underlie the main valley terrace and the valley axis deposits are preserved as inset fill terraces historical arroyo cutting then formed a 65 km long arroyo ca 150 yr b p based on correlation to regional paleoclimate records channel aggradation occurred during periods of relative aridity and low peak discharge events while wet periods possibly floods after drought led to fluvial incision these cycles are superimposed on a transition from a wide silt and fine sand dominated fluvial system to a modern narrow sand and gravel dominated arroyo channel the relationship between times of fluvial process change and climate change in cuyama valley bears considerable similarity to other well studied dryland rivers in the southwestern united states however the complex sedimentology and geometry of preserved fluvial deposits suggest that a wider range of fluvial modes occurred along the cuyama river than has been reported in simpler cut and fill dominated channels elsewhere these spatial and sedimentological complexities underscore the need to link fluvial deposits and their bounding unconformities along a channel in order to fully understand the spatial and temporal evolution of ancient fluvial systems

linking environmental regimes space and time interpretations of structural and functional connectivity connectivity as a concept has been increasingly part of discussions or explanations in hydrology geomorphology and ecology we address recent critiques of this approach by demonstrating how a refinement which distinguishes structural connectivity from functional connectivity can be used to explain patterns observed in very different environmental systems these systems are found in linkages between surface and subsurface flowpaths and the hyporheos in the river don a temperate river channel in yorkshire uk in surface and subsurface fluxes in agricultural land in the uk and in vegetation and surface conditions in a degrading environment at the sevilleta lter site in the semi arid southwest usa first we demonstrate long term geological and structural controls mediated by in channel processes second human organization of landscape elements is a significant control on runoff and erosion so that similar events can produce very different responses and vice versa third linkages between the removal of grass vegetation and runoff and erosion produce non linear and path dependent feedbacks which control the subsequent degradation of the landscape making the process difficult to reverse as a result of these studies we argue that even in cases where connectivity cannot be directly quantified at least at present this limitation does not prevent the concept from being a useful heuristic device for exploring responses of complex systems furthermore this result implies that an increasing need exists for disciplinary connectivity to investigate such systems

episodic sediment accumulation on amazonian flood plains influenced by el nino southern oscillation continental scale rivers with a sandy bed sequester a significant proportion of their sediment load in flood plains the spatial extent and depths of such deposits have been described and flood plain accumulation has been determined at decadal timescales but it has not been possible to identify discrete events or to resolve deposition on near annual timescales here we analyse 210 pb activity profiles from sediment cores taken in the pristine beni and mamore river basins which together comprise 720 000 km2 of the amazon basin to investigate sediment accumulation patterns in the andean amazonian foreland we find that in most locations sediment stratigraphy is dominated by discrete packages of sediments of uniform age which are typically 20 80 cm thick with system wide recurrence intervals of about 8 yr indicating relatively rare episodic deposition events ocean temperature and stream flow records link these episodic events to rapidly rising floods associated with la nina events which debouch extraordinary volumes of sediments from the andes we conclude that transient processes driven by the el nino southern oscillation cycle control the formation of the bolivian flood plains and modulate downstream delivery of sediments as well as associated carbon nutrients and pollutants to the amazon main stem

subglacial meltwater channels and glaciofluvial deposits in the kimberley basin western australia 1 8 ga low latitude glaciation coeval with continental assembly a late palaeoproterozoic unconformity surface developed on low dipping sandstone in the kimberley region northwestern australia exhibits numerous linear parallel grooves 10 50 mm deep 40 80 mm wide and tens of metres long and other erosional forms including sichelwannen these features are interpreted as nye channels and sculpted forms eroded by subglacial meltwaters sandstone filled cracks exposed at the unconformity are viewed as periglacial frost fissures an overlying conglomerate facies 1 15 m thick at the base of the c 1800 ma king leopold sandstone kimberley basin succession contains poorly sorted pebble to boulder conglomerate and is interpreted as glaciofluvial in origin the orientation of the nye channels and sculpted forms and the palaeocurrent direction for the glaciofluvial deposits indicate westward ice flow the conformably following locally glauconitic quartzarenite of the king leopold sandstone probably accumulated in an epeiric sea implying that glaciation reached close to sea level transgression in northwestern and central australia at c 1800 ma may have been partly glacio eustatic glaciation was initiated to the east of the kimberley basin evidently in the halls creek orogen during a major phase of continental collision in australia and worldwide supercontinental assembly recognition of the king leopold glaciation which occurred in low palaeolatitudes c 2200 and 800 ma

avulsion regimes in southeast texas rivers avulsions relatively sudden changes in course or establishment of new anabranches are an important process in alluvial rivers their key role in floodplain construction and alluvial architecture and the general conditions favouring avulsions are well known however avulsion processes and evolution and the factors controlling avulsion regimes are poorly understood in the southeast texas coastal plain where avulsions are common features of the river valleys avulsions were studied on the lower brazos navasota trinity neches and sabine rivers using a combination of aerial imagery digital elevation models and field surveys avulsions have important influences on the surface morphology and contemporary processes in all five rivers features associated with avulsions are active and distinct throughout the study area and all the rivers have experienced geologically if not historically recent avulsions however no two of the study rivers have the same contemporary avulsion regime first order differences in avulsion style are controlled by the stage of valley filling and within the three rivers characterized by an unfilled incised valley antecedent morphology associated with late quaternary and holocene coastal and fluvial deltaic processes accounts for the major differences in the navasota 27 avulsions in 185 km and neches 21 in 340 km rivers subchannels associated with avulsions exist in all stages of development from active to infilled and some have occurred in recent decades the other rivers have fewer avulsions but both the sabine and trinity have experienced historic channel shifts only the brazos river has experienced no avulsions within the past c 300 years results show that even within a region of similar environmental controls and geological history local variations in inherited morphology can result in different avulsion regimes copyright 2008 john wiley sons ltd