paleohydrology of the upper miocene bicorb lake eastern spain as inferred from stable isotopic data from inorganic carbonates abstract the hydrological evolution of the upper miocene bicorb lake eastern spain has been established based on sedimentology carbonate mineralogy and stable isotopic data from inorganic carbonates from the upper lacustrine unit three main subunits have been recognized in subunit a the sedimentological features suggest a hydrologically closed lake although the isotopic data are not conclusive the isotopic compositions of primary carbonates from subunit b display a distribution typical for a hydrologically closed lake and allow the differentiation of four developmental stages the first stage was defined by the deposition of gypsum lmc dolomite and aragonite indicating large variations in the water mg ca ratio during the second and third stages only lmc was deposited suggesting only minor mg ca fluctuations the 13c and 18o pattern of the second stage shows a well defined covariance r 0 8 while in the third stage the isotopic data display a negative covariant relationship r 0 8 changes in dissolved inorganic carbon composition are considered the main factor to explain the variations from positive to negative covariance in the fourth stage the lake waters underwent large mg ca fluctuations as indicated by the deposition of lmc hmc and aragonite the isotopic trend is also covariant finally subunit c is characterized by lmc and minor amounts of hmc suggesting minor changes in mg ca ratio the isotopic features of this subunit are more congruent with a hydrologically open lake the lowest 13c and 18o values are very similar in the three subunits reflecting the most dilute conditions of the lake water and a uniform isotopic composition of the local meteoric water during these periods the changes in water balance and solute inputs recorded in the mineralogy and isotopic signatures of carbonates were controlled by the diapiric evolution and changes in the e p balance

modelling of magnetic data for scaling geology interpretation of magnetic data can be carried out either in the space or frequency domain the interpretation in the frequency domain is computationally convenient because convolution becomes multiplication the frequency domain approach assumes that the magnetic sources distribution has a random and uncorrelated distribution this approach is modified to include random and fractal distribution of sources on the basis of borehole data the physical properties of the rocks exhibit scaling behaviour which can be defined as p k ak where p k is the power spectrum as a function of wave number k and a and are the constant and scaling exponent respectively a white noise distribution corresponds to 0 the high resolution methods of power spectral estimation e g maximum entropy method and multi taper method produce smooth spectra therefore estimation of scaling exponents is more reliable the values of are found to be related to the lithology and heterogeneities in the crust the modelling of magnetic data for scaling distribution of sources leads to an improved method of interpreting the magnetic data known as the scaling spectral method the method has found applicability in estimating the basement depth curie depth and filtering of magnetic data

sediment trapping characteristics of a pit trap and the helley smith sampler in a cobble gravel bed river 1 although designed for granule gravels the helley smith hs bed load sampler is often used in streams with much coarser beds to compare magnitudes and grain size distributions of sediment samples collected by a pit trap and a standard hs sampler we conducted 22 sampling events over a wide range of flows during a snowmelt freshet in a stream with a coarse gravel bed each sampling event consisted of three simultaneous measurements one made with a pit trap installed in the bed one with a hs sampler placed on the bed directly beside the pit trap hs i and one with a hs sampler placed on the downstream rim of the pit trap hs p we summed the catches of the pit trap and hs p to estimate actual bed load transport the pit trap and hs i catches were then compared to the summed sample the pit trap yielded a remarkably consistent positively skewed sigmoidal distribution of catch efficiency for all 22 measurements with near 100 efficiency for material larger than 2 8 mm the hs i sampler was more variable in its catch and trapping efficiency exhibiting low trapping efficiency for midrange material 0 71 to 16 mm but high efficiency for finer material the results cast doubt on the accuracy of bed load data sets collected by helley smith samplers in coarse gravel channels

oxygen and carbon isotope trends and sedimentological evolution of a meromictic and saline lacustrine system the holocene medicine lake basin north american great plains usa abstract the succession of sedimentary subfacies in the medicine lake basin south dakota usa documents numerous changes in total dissolved solids tds lake level and the nature and stability of meromixis during the holocene the lake formed about 10 6 ka b p when coarse clastics and massive fine grained muds were deposited in a well mixed freshwater system subsequently the lake became saline and meromictic depositing a finely laminated unit composed of variegated and gray muds organic facies gypsum and aragonite laminae phototrophic bacterial plate communities bpc at the chemocline were significant producers of pelagic organic matter relatively high lake levels at least 10 m higher than today but saline and meromictic conditions predominated through the early to mid holocene at the end of this phase lake level dropped and stable meromixis was disrupted sands and massive or banded muds were deposited in sublittoral areas and benthic microbial communities bmc spread over the lake replacing bpcs as the predominant microbial producers when lake level rose again massive and laminated units were deposited under less saline conditions another pronounced episode of low lake level and high salinity followed the most recent sediments are sapropels massive or banded muds and littoral sands the 18o record from authigenic aragonite shows more positive values during the arid mid holocene interval with an abrupt increase at the end of this period followed by generally more negative values during the cooler and wetter late holocene the small range of 18o values 3 suggests that the lake was well buffered against high frequency climatic cycles probably as a result of groundwater modulation we postulate that meromixis and the type of photosynthetic microbial communities dominating the basinal region of the lake system either bpcs or bmcs exerted major controls on the carbon cycle and consequently on the development of isotopic trends linking 13c and 18o values more negative 13c values during the early and mid holocene are interpreted as a consequence of the predominance of 12c enriched microbial carbon from bpcs examples of both covariant and inverse covariant isotope trends between 13c and 18o values occur in the medicine lake record inverse covariant trends characterize long periods of stable meromixis when bpcs predominate over bmcs we hypothesize that well developed water stratification caused by greater influx of relatively 18o depleted freshwater induces higher productivity at the chemocline and consequently more positive 13c values in the precipitated carbonates unstable phases of meromixis or holomictic conditions are characterized by a predominance of bmcs or other biogenic producers over bpcs and a number of other factors combine to promote covariant trends the medicine lake record is consistent with the paleoclimatic interpretation for the northern great plains of a more arid early and middle holocene followed by an abrupt transition to a relatively cooler and wetter late holocene the sedimentary succesion in medicine lake documents a much more fluctuating and abrupt climate behavior than suggested by the vegetation paleorecord and suggest a late holocene climate punctuated by arid episodes

a comparison between flume and field bed load transport data and consequences for surface based bed load transport prediction 1 the ability of simple equations to predict bed load transport with limited knowledge of the bed surface material was investigated this was done using a data set consisting of 7 636 bed load transport values from the flume 1 317 data and from 84 river reaches 6 319 field data it was possible to collapse field and flume data by correcting the ratio between the shields number and its critical value with a very simple hiding function proposed as a power law of the d84 d50 ratio in so doing a surface based bed load transport formula was proposed it was successfully tested on an independent data set comprising sand and gravel bed rivers with slope in the range 0 0002 0 08 with 86 of the values predicted within a precision of 1 order of magnitude moreover the formula reproduced the low transport rates well contrary to the usual surface based formulas also tested and is particularly well suited for estimating low transport rates associated with near bankfull flow discharge this new formula is neither time consuming no fractionwise calculation nor data consuming the required parameters are the flow discharge the active width the slope and the surface grain diameters d50 and d84

controls over particle motion and resting times of coarse bed load transport in a glacier fed mountain stream coarse bed load transport is a crucial process in river morphodynamics but is difficult to monitor in mountain streams here we present a new sediment transport dataset obtained from two years of field based monitoring 2014 2015 at the estero morales a high gradient stream in the central chilean andes this stream features step pool bed geometry and a glacier fed hydrologic regime characterized by abrupt daily fluctuations in discharge bed load was monitored directly using bunte samplers and by surveying the mobility of pit passive integrated transponder tags we used the competence method to quantify the effective slope which is the fraction of the topographical slope responsible for bed load transport this accounts for only 10 of the topographical slope confirming that most of the energy is dissipated on macroroughness elements we used the displacement lengths of pit tags to analyze displacement lengths and virtual velocity of a wide range of tracer sizes 38 415 mm bed load transport in the estero morales show to be size selective and the distance between steps influences the displacement lengths of pit tags displacement lengths were also used to derive the statistics of flight distances and resting times our results show that the average length of flight scales inversely to grain size this contradicts einstein s conjecture about the linear relationship between grain size and intervals between resting periods in a steep step pool stream in ordinary flood conditions

dynamics of bedload transport in turkey brook a coarse grained alluvial channel automatic and continuously recording samplers are deployed in a hertfordshire gravel bed stream to show that bedload transport is related to stream power the pattern is similar to that already established for north american channels but because the record is so detailed it is possible to identify the cause of the considerable scatter that is normal in such relationships a major factor is the occurrence of rhythmic pulses in bedload discharge that are not matched by similar fluctuations in hydraulic variables it is suggested that these pulses reflect downstream differences in the concentration of mobile particles in a slow moving traction carpet and that they may be likened to kinematic waves the record also reveals that the threshold of sediment transport always presumed hithero to be associated with incipient motion is related to the cessation of bedload transport in a river flood indeed the mean value of stream power at the finish of bedload transport is only 20 percent of that prevailing at the moment of incipient sediment motion because of this there is an inevitably poor correlation between actual bedload transport rates and those predicted by bedload equations which rely upon a single traction threshold these new data show that the general inverse relationship between bedload discharge and water depth grain size ratio proposed by bagnold 1977 1980 is not universal transport efficiency for this gravel bed stream is typically 0 05 per cent of available stream power which compares with 1 6 per cent for a river moving both gravel and sand and 5 per cent for another channel where bedload is composed predominantly of sand sized particles it is argued that coarse and fine grained alluvial channels may need to be considered separately by allowing for differences in traction threshold at the beginning and end of bedload events and by averaging bedload discharge flood by flood in order to smooth out the effect of pulses it is possible to achieve a reasonably good prediction of average bedload transport rate in terms of stream power

marginal bed load transport in a gravel bed stream sagehen creek california marginal bed load transport describes the condition when relatively few bed particles are moving at any time bed particles resting in the shallowest bed pockets will move when the dimensionless shear stress exceeds a value of about 0 020 as increases the number of bed particles moving increases significant motion of bed particles i e when a substantial fraction of the bed particles are moving occurs when exceeds a value of about 0 060 thus marginal bed load transport occurs over the domain 0 020 0 060 marginal bed load transport rates and associated hydraulic characteristics of sagehen creek a small mountain gravel bed stream were measured on 55 days at discharges ranging from slightly less than one half of the bank full discharge to more than 4 times the bank full discharge dimensionless shear stress varied from 0 032 to 0 042 and bed particles as large as the 80th percentile of the bed surface were transported the relation between reference dimensionless shear stress and relative particle protrusion for sagehen creek was determined by varying ri to obtain the best fit of the parker bed load function to the measured transport rates during the period of record water years 1954 1991 the mean annual quantity of bed load transported past the sagehen creek gage was 24 7 tons forty seven percent of all bed load transported during the 38 years of record occurred in just 6 years during 10 of the 38 years of record essentially no bed load was transported the median diameter of bed load was 26 mm compared to 58 mm in the surface bed material

the nature of the non gaussianity of primary reflection coefficients and its significance for deconvolution one of the important properties of a series of primary reflection coefficients is its amplitude distribution this paper examines the amplitude distribution of primary reflection coefficients generated from a number of block averaged well logs with block thicknesses corresponding to 1 ms two way time the distribution is always essentially symmetric but has a sharper central peak and larger tails than a gaussian distribution thus any attempt to estimate phase using the bi spectrum third order spectrum is unlikely to be successful since the third order moment is almost identically zero complicated tri spectrum fourth order spectrum calculations are thus required minimum entropy deconvolution med schemes should be able to exploit this form of non gaussianity however both these methods assume a white reflectivity sequence they would therefore mix up the contributions to the trace s spectral shape that are due to the wavelet and those that are due to non white reflectivity unless corrections are introduced a mixture of two laplace distributions provides a good fit to the empirical amplitude distributions such a mixture distribution fits nicely with sedimentological observations namely that clear distinctions can be made between sedimentary beds and lithological units that comprise one or more such beds with the same basic lithology and that lithological units can be expected to display larger reflection coefficients at their boundaries than sedimentary beds the geological processes that engender major lithological changes are not the same as those for truncation of bedding analyses of sub sequences of the reflection series are seen to support this idea the variation of the mixing proportion parameter allows for scale and shape changes in different segments of the series and hence provides a more flexible description of the series than the generalized gaussian distribution which is shown to also provide a good fit to the series both the mixture of two laplace distributions and the generalized gaussian distribution can be expressed as scale mixtures of the ordinary gaussian distribution this result provides a link with the ordinary gaussian distribution which might have been expected to be the distribution of a natural series such as reflection coefficients it is also important in the consideration of the solution of med type methods it is shown that real coloured primary reflection series do not seem to be obtainable as the deconvolution result from med type deconvolution schemes

bedload transport rates for coarse bed streams in an atlantic region narcea river nw iberian peninsula abstract rivers from northern cantabrian mountain range nw spain are emplaced in an atlantic region draining to the bay of biscay and saving 2000 m in a short path thus high gradient streams normally develop with coarse bed sediment and a strong importance of bedload transport processes in their morphosedimentary dynamics in the present work tagged clasts painted and with inserted magnets were used as tracers in order to estimate bedload transport rates in two of those coarse bed streams river piguena and river coto belonging to river narcea drainage basin four methodological steps were followed 1 grain size analysis of bed sediment 2 preparing tracer clasts in the laboratory 3 seeding the studied reaches with the tracers measuring their displacements after flood events and 4 analysis of data ten flood episodes with the ability to disturb tracer position were registered along two hydrological years 2009 2010 and 2010 2011 bedload transport rates were estimated for six of these episodes values ranging from 1 1 to 4 1 kg s were obtained for piguena and values ranging from 0 20 to 0 28 kg s were obtained for coto also an attempt at analysis of threshold conditions was tried and a regression model between bedload transport rates and shear stress was built

sedimentology and isotope geochemistry of lacustrine carbonates of the oligocene campins basin north east spain the non marine campins basin developed in the oligocene during a period of early rifting of the catalan coastal ranges lacustrine deposits interbedded between two alluvial units comprise shallow and deep lacustrine facies the lower shallow lacustrine facies are made up of microbialite buildups and thin limestone beds in the studied area these facies are overlain by deep lacustrine facies which consist of alternations of several metre thick carbonate and mudstone dominated intervals in addition to calcite which is characteristic of the shallow lacustrine facies aragonite and abundant dolomite are present in the deep lacustrine facies this mineralogical change in the sequence reflects an overall increase in the mg ca ratio of the lake waters the deep lacustrine sequences are interpreted as having formed in a hydrologically closed basin that was subject to changes in the mg ca ratio of the water probably related to variations in the evaporation precipitation rate the sedimentological mineralogical and isotopic characteristics of the campins basin dolomites suggest that in general they are primary in origin the stable isotope data show an approximate covariance between 13c and 18o in the lower shallow lacustrine carbonates calcite which suggests that they formed during the onset of closure of the lake the 13c and 18o values of the deep lacustrine carbonates display three different clusters that are roughly related to the carbonate mineralogy normalisation with respect to calcite of the isotopic compositions of dolomite and aragonite from the deep lacustrine carbonates allows the integration of all these isotope values into one covariant trend the sequential appearance of different carbonate minerals and the isotopic covariant trend may indicate an overall evaporative concentration of the lake waters the change in slope of the covariant trend for the isotope values between the shallow and the deep lacustrine carbonates might reflect the change in the waterbody morphology recorded in the basin fill sequence

the broad band fractal nature of heterogeneity in the upper crust from petrophysical logs in situ measurements of petrophysical properties of the upper crust from wire line logs provide a direct means of assessing fluctuations in these properties with depth and thus allow for the statistical characterization of crustal heterogeneity wire line logs from a cluster of nine boreholes 1000 1500 m deep have been analysed using four different techniques autocorrelation semi variogram rescaled range and power spectra six of the boreholes are vertical the remainder inclined all penetrate clastic and pyroclastic rock the analysis techniques have been tested on synthetic data for which we have precise control on the scaling in order to assess their robustness the results for the borehole data show broad band fractal scaling with a fractal dimension of 1 62 to 1 97 autocorrelation 1 59 to 1 79 rescaled range and 1 61 to 2 0 power spectra the use of different techniques to estimate the fractal dimension provides an excellent constraint on the results furthermore it allows us to determine which model for crustal heterogeneity best describes the data a band limited von karman function or unbounded fractal scaling in order to test the possible anisotropy in the scaling parameters the horizontal scaling properties for this area have been calculated by correlation spectra analysis of neighbouring wells this suggests that upper crustal correlation lengths are of the order of kilometres and anisotropic being over four times greater in the horizontal direction the origins of the observed power law scaling are complex analysis of long term correlations between logs and televiewer data points towards the influence of fracture porosity within the pyroclastics but a fractal distribution of pore spaces within the clastics also controls the log fluctuations separating the logs into clastic and pyroclastic subsets reveals slight differences in fractal scaling as determined by autocorrelation and semi variogram these differences are attributed to the dominance of either primary or fracture porosity within each geological unit

cross channel patterns of bed material transport in a poorly sorted sand bed channel abstract understanding of sediment transport comes largely from studies conducted on well sorted sand bed and poorly sorted gravel bed channels the aim of this study is to evaluate cross channel patterns of transport rate and grain size in a poorly sorted sand bed channel transport observations were collected from the san antonio river using a helley smith sampler during flows from 0 02 to 1 1 times bankfull capacity resulting transport rates and grain size distributions were pooled to describe eight sections across a channel transect that includes the lower bank and compared to local boundary material maximum transport rates are concentrated in the central zone of the streambed regardless of flow level but gravels and coarse sands are conveyed preferentially on one side of the bed grain size distributions change relatively little with flow and approximate the local bed material supply the size distributions associated with smaller transport rates near the channel margin become finer and more closely approximate the size characteristics of bank material at higher flows results extend patterns of differential routing of grain sizes to channel banks and establish the relative fluxes between the bed and bank environments the small gravel content in poorly sorted sand beds requires further attention because it can contribute to cross channel variation in sediment fluxes limit the development of sandy bedforms and influence the quality of streambed habitat

polyphase deformation of diapiric areas in models and in the eastern prebetics spain fingerlike bodies of evaporite rocks have been observed in many regions affected by multiple tectonic phases such as the atlas the pyrenees or the zagros mountains where they have been interpreted as fault plane diapiric injections or collapse related salt welds in this article we suggest a new interpretation of these structures as squeezed diapirs based on detailed structural and sedimentological field data of the bicorb quesa diapir eastern prebetics and offer five analog models which simulate the polyphase deformation of the eastern prebetics in this area diapirs formed from the oligocene to langhian during an extensional phase related to the opening of the valencia trough these diapirs were later affected by a serravallian contractional phase which inverted the preexisting grabens and created new folds and thrusts the preexisting diapirs were necked and or squeezed forming secondary welds with a fingerlike geometry that isolated the diapir bulbs from their source layer extrusion of diapiric material was also accelerated during this phase but no new diapirs formed finally the area was again affected by an extensional phase during the tortonian which reactivated the normal faults and created a new set of diapirs the new diapirs formed where the overburden was thinner that is at the toe of the major reactivated faults commonly these faults coincide with the bounding faults of the major grabens formed during the first extensional phase and therefore the new diapirs grow close to the location of the squeezed diapirs the models also show that the faults created during the initial extension prevailed as the main focus for deformation during the polyphase history deformation in the overburden and the viscous layer was mainly accommodated along the major grabens formed during the first extensional stage during shortening the initial major grabens deformed as complex anticlines and during the subsequent extensional phase most deformation occurred by the collapse of these anticlines along preexisting faults fault welds and the flank of the squeezed diapirs the source layer is compartmentalized accumulating and withdrawing material in the same locations the initial grabens and horst as a result the source layer is easily depleted beneath the initial horst forming primary welds

a general power equation for predicting bed load transport rates in gravel bed rivers 1 a variety of formulae has been developed to predict bed load transport in gravel bed rivers ranging from simple regressions to complex multiparameter formulations the ability to test these formulae across numerous field sites has until recently been hampered by a paucity of bed load transport data for gravel bed rivers we use 2104 bed load transport observations in 24 gravel bed rivers in idaho to assess the performance of eight different formulations of four bed load transport equations results show substantial differences in performance but no consistent relationship between formula performance and degree of calibration or complexity however formulae containing a transport threshold typically exhibit poor performance furthermore we find that the transport data are best described by a simple power function of discharge from this we propose a new bed load transport equation and identify channel and watershed characteristics that control the exponent and coefficient of the proposed power function we find that the exponent is principally a factor of supply related channel armoring transport capacity in excess of sediment supply whereas the coefficient is related to drainage area a surrogate for absolute sediment supply we evaluate the accuracy of the proposed power function at 17 independent test sites

deep to shallow lacustrine evaporites in the libros gypsum southern teruel basin miocene ne spain an occurrence of pelletal gypsum rhythmites abstract a number of non marine evaporite units composed of primary gypsum were deposited in saline lakes that developed in the southern teruel basin ne spain during the miocene in the basin depocentre a continuum of lacustrine evaporite lithofacies influenced by the activity of organisms is displayed the libros gypsum was deposited in a deep lake in which water stratification became unstable with progressive shoaling rhythmites composed of laminae of pelletal gypsum and laminae of very fine lenticular gypsum crystals mixed with siliceous microorganisms formed in addition to gypsum turbidites intraformational gypsum breccias and slump structures the pelletal laminae originated from the faecal activity of animals crustaceans ingesting gypsum crystallites in the lake water during episodes of maximum evaporation whereas the laminae of very fine lenticular gypsum mixed with microorganisms accumulated during episodes of relative dilution in the wide marginal zones of the basin the libros gypsum unit consists of massive to thin bedded bioturbated gypsum and thin bedded clotted gypsum which formed in intermediate to very shallow palustrine water depths the bioturbated gypsum lithofacies were produced by the action of diverse organisms presumably worms and coleopterans and chironomid larvae to a lesser extent the massive lithofacies precipitated in very shallow water and the thin bedded lithofacies formed in shallow to deeper settings the thin bedded clotted gypsum is a relatively deep facies that may have diverse origins e g bioturbation compaction disruption of soft sediments and early diagenesis there is a well developed metre scale cyclicity in the marginal lake sequences which is not observed in the inner lake deposits this suggests a depth control in the various lacustrine subenvironments to record cyclic evaporitic processes the isotopic composition of the gypsum indicates early sulphate reducing bacterial activity in the bottom of the lake and suggests that the sulphate was derived from the chemical recycling of triassic evaporites of the country rocks

use of charophyte carbonates as proxy indicators of subtle hydrological and chemical changes in marl lakes example from the miocene bicorb basin eastern spain abstract the lower alluvial unit in the miocene bicorb basin contains several metric scale limestone intervals which record episodic shallow lacustrine environments in an alluvial setting developed during the early stage of the basin s evolution five main carbonate facies have been differentiated in the lacustrine limestones although calcite charophyte incrustations predominate and constitute the most striking features of these deposits the thinnest limestone intervals correspond to deposits from charophyte meadows in ponded shallow depressions in floodplains the thickest limestone intervals are mainly formed by banded limestones and usually correspond to diverse types of regressive sequences that have been interpreted as resulting from the infill of shallow lakes the sedimentological features and sequences show noticeable differences in the gradient of the littoral zones and the amount of palustrine deposits with models proposed for marl lakes charophytic carbonates from the best preserved facies show similar microtextures to those from recent charophyte incrustations the variations in stable isotopes 13 c 18 o for these primary carbonates occur in parallel with luminescence variations and correspond to hydrological changes and variations in solute composition and eh ph status in the lake waters the carbonates that display moderate to strong diagenetic modifications show a diverse degree of compaction aggrading neomorphism strong cementation and nodulization the isotopic values for these are arranged in diverse clusters there is a correlation between the degree of luminescence and the 13 c this suggests that hydrological and hydrochemical variations both in the lacustrine and diagenetic environments are being recorded in parallel we emphasize the need for further comparative studies between recent and ancient charophytic carbonates as these carbonates have been used in palaeoenvironmental reconstructions special attention must be paid to the diagenetic changes in ancient charophytic marls

rise closure and reactivation of the bicorb quesa evaporite diapir eastern prebetics spain the bicorb quesa diapir belongs to a complex system of evaporite diapirs located in the se iberian peninsula it was emplaced along the axis of a graben system flanked by two syn diapir growth basins filled by miocene sediments the miocene evolution of the diapir may be divided into three major phases an initial extensional phase during which the graben system formed and the diapir rose a second phase during which regional shortening closed the diapir and a third phase characterized by normal faulting during which diapirism was reactivated cutting the previously formed thrusts and folds this evolutionary trend demonstrates that diapirism was initiated and promoted by regional extension during the two extensional phases the diapir grew by reactive active and passive rise sedimentation during the reactive stage was characterized by strong basin subsidence sharp changes in sediment thicknesses and major coarse grained sediment input during the active stage the coeval basin fill sequence displays progressive angular unconformities gravitational deposits and subtle changes in thickness with the sediments unconformably overlying most of the earlier formed faults finally during the passive stage the sediments synchronous with diapir formation include abundant components from the extruding rocks and show gentler changes in thicknesses a progressive decrease in the input of coarse sediments and the deposition of mudstones and or lacustrine carbonates that clearly extend onto the faulted basin margins

the effect of hydrographs on bed load transport and bed sediment spatial arrangement 1 field measurements of sediment transport in gravel bed rivers often reveal hysteretic effects due to differences in sediment availability between the rising and falling limbs of a flood hydrograph however only a small number of flume studies have analyzed the dynamics of sediment transport during hydrographs three types of stepped hydrographs with contrasting durations and magnitudes are simulated here under sediment recirculation conditions bed load transport rate and grain size have been measured continuously the dynamic behavior of the surface armor layer has been explored by analyzing digital photographs and laser scanner surveys of the bed surface taken during hydrographs the results indicate that sediment transport during the falling limb was lower than during the rising limb in all of the three types of hydrographs this reduction is more evident for the low magnitude hydrographs the grain size of the bed remained virtually constant throughout the hydrographs but the grain size of transported sediments exhibited a counterclockwise hysteresis also a significant increase in the reference shear stress for sediment entrainment was measured during the falling limb of hydrographs additionally a detailed analysis of partial transport dynamics of the bed surface sediments reveals a reduction in sediment mobility during the falling limb of the hydrographs the difference in sediment entrainment and transport before and after the peak of the hydrographs appears to be caused by a change in the organization of the surface sediments an analysis of detailed laser scan bed surveys reveals a phase of bed restructuring lower vertical roughness clast rearrangement during the falling limb of hydrographs consequently changes in the degree of organization and complexity of the bed surface are likely the cause of the reduced mobility of sediments and thus of the reduced sediment transport rate during the falling limb of the hydrographs

sedimentary facies depositional environments and palaeogeographic evolution of the neogene denizli basin sw anatolia turkey abstract the denizli basin southwestern anatolia turkey contains a record of environmental changes dating since the early miocene detailed facies analysis of the neogene formations in this half graben enables us to document successive depositional regimes and palaeogeographic settings sedimentation commenced in the early miocene with the deposition of alluvial fan and fluvial facies kizilburun formation at this stage alluvial fans sourced from elevated areas to the south prograded towards the basin centre the middle miocene time saw the establishment of marginal lacustrine and wetland environments followed by the development of a shallow lake sazak formation the uppermost part of this unit consists of evaporitic saline lake and saline mudflat facies that grade upward into brackish lacustrine deposits of late miocene pliocene age kolankaya formation the lake became shallower at the end of the pliocene time as is indicated by expansion shoreface foreshore facies in the early quaternary the denizli basin was transformed into a graben by the activation of ese trending normal faults alluvial fans were active at the basin margins whereas a meandering river system occupied the basin central part oxygen isotope data from carbonates in the successive formations show an alternation of wetter climatic periods when fresh water settings predominated and very arid periods when the basin hosted brackish to hypersaline lakes the neogene sedimentation was controlled by an active ese trending major normal fault along the basin s southern margin and by climatically induced lake level changes the deposition was more or less continuous from the early miocene to late pliocene time with local unconformities developed only in the uppermost part of the basin fill succession the unconformable base of the overlying quaternary deposits reflects the basin s transformation from a half graben into a graben system

limnic food web and salinity of the upper miocene bicorb palaeolake eastern spain abstract in an attempt to arrive at a preliminary reconstruction of the limnic food web of the upper miocene bicorb basin eastern spain and to obtain new palaeontological information regarding the salinity of its palaeolake studies were made of the fossil assemblages of aquatic organisms in the outcrops of facies associations 2 and 3 subunit b of the upper unit established in 1998 by anadon et al these outcrops known as venus cantera and bicorb insectos 1 and 3 are typical konservat lagerstatten we here describe four specimens of a new species of the cyprinodontid genus aphanius a bicorbensis sp nov plus several chironomid insects and coprolites mainly from the venus outcrop two morphotypes of chironomid pupal exuviae were found both of which were attributed to the subfamily chironominae the larger morphotype was attributed to chironomus sp tribe chironomini and the smaller to tanytarsini gen et sp indet coprolites were separated into two types c1 and c2 based on their contents i e the remains of chironomids or miliolid foraminifers respectively the miliolid foraminifers belonged to the family hauerinidae possibly to the genus quinqueloculina it is concluded that aphanius fish were second level consumers feeding on chironomids and miliolid foraminifers primary producers were mainly represented by the aquatic plant potamogeton botryococcus green algae and microbial mats almost certainly photosynthetic this notably simple limnic food web and this aquatic fossil assemblage suggest that the bicorb palaeolake was saline or brackish the living taxa related to this assemblage are notably tolerant of high salinity this salinity is related to the presence of a triassic diapir on the southern side of the bicorb basin in addition non bioturbated finely laminated calcareous mudstones and exceptionally well preserved delicate insects indicate the lake water to have shown a halocline leading to meromictic episodes with the development of microbial mats at the lake bottom

the use of short lived radionuclides to quantify transitional bed material transport in a regulated river we investigate the use of the short lived fallout radionuclide beryllium 7 7be t1 2 53 4 days as a tracer of medium and coarse sand 0 25 2 mm which transitions between transport in suspension and as bed load and evaluate the effects of impoundment on seasonal and spatial variations in bed sedimentation we measure 7be activities in approximately monthly samples from point bar and streambed sediments in one unregulated and one regulated stream in the regulated stream our sampling spanned an array of flow and management conditions during the annual transition from flood control in the winter and early spring to run of the river operation from late spring to autumn sediment stored behind the dam during the winter quickly became depleted in 7be activity this resulted in a pulse of dead sediment released when the dam gates were opened in the spring which could be tracked as it moved downstream measured average sediment transport velocities 30 80 metres per day m d 1 exceed those typically reported for bulk bed load transport and are remarkably constant across varied flow regimes possibly due to corresponding changes in bed sand fraction results also show that the length scale of the downstream impact of dam management on sediment transport is short c 1 km beyond this distance the sediment trapped by the dam is replaced by new sediment from tributaries and other downstream sources copyright 2006 john wiley sons ltd

sedimentation in lake malawi east africa during the past 10 000 years a continuous paleoclimatic record from the southern tropics a suite of piston cores recovered from lake malawi 9 14 s 34 35 e east africa in 1986 has been analyzed for major and minor elements organic c and n calcium carbonate and diatoms an internally consistent stratigraphy was constructed from calcium carbonate abundance and variations in the two most abundant diatom genera stephanodiscus and melosira with age control obtained primarily from 14c dating of the carbonate differences with time in fe abundance in a transect of cores from different water depths have been interpreted to reflect changes in chemocline depth the depth to the chemocline was on the order of 100 m shallower than present prior to 3500 yr b p indicating less seasonality carbonate production and preservation appears to be related to climatically induced changes in both salinity and chemical distributions in the water column the carbonate which precipitates from surface waters is most abundant during the interval from about 10 000 to 6000 yr b p this micrite most likely represents periods of low lake level when salinity increased and carbonate precipitation was enhanced sedimentary evidence suggests that lake levels were 100 150 m lower than present during this period this record is different from climatic trends in northern intertropical africa but appears to also be related to changes in insolation and monsoon circulation this is the northernmost basin in africa reported to exhibit a southern hemisphere response to the early holocene northern hemisphere summer insolation maximum the climatic hingeline north of lake malawi 9 s implied by our results is significantly south of that indicated by general circulation model simulations however the cores show evidence for periods of abrupt climate change during the interval of generally arid climate

facies relationships and sedimentation in large rift lakes and implications for hydrocarbon exploration examples from lakes turkana and tanganyika abstract two african lakes turkana and tanganyika illustrate a spectrum of sediments and facies architectures which can occur in large rift lacustrine basins they demonstrate contrasts between sediments deposited in a semi arid moderately deep mainly volcanic basin turkana and a semi humid extremely deep basin without significant volcanism tanganyika turkana deposits are dominated by rapidly accumulating organic poor terrigenous muds coarse clastic input is in part limited by ponding in marginal subbasins due to volcanic barriers profundal coarse clastic deposition is rare sediments contain little biogenic components except in the sediment starved south basin sediments are also poor in cartonates tanganyika deposits are dominated by organic rich biogenic muds steep fault escarpments and uniform slopes along shelf platform and rift axis lake margins promote the efficient transport of sands into profundal settings total clastic sediment supply into the basin is severely restricted by basin morphology with steep relief backslopping a limited drainage basin area and presettling in upstream lake kivu sediment ponding along margins is rare littoral carbonates are common a consequence of low net clastic sedimentation rates many of the differences between facies in the two lakes can be explained by contrasts in basin margin slope and relief volcanic activity and climate between the two lakes the results of this study suggest that lake deposits formed in tanganyika type rift basins are more appropriate exploration target for hydrocarbon exploration than those from turkana type basins

sediment transport in a large impounded river the lower ebro ne iberian peninsula abstract the sediment transport of the highly regulated lower ebro river is estimated on the basis of a measuring programme carried out between 2002 and 2004 total sediment transport including both suspended load and bedload was measured upstream and downstream from the mequinenza and riba roja reservoirs with special attention to the transport during floods annual total load upstream from the dams is estimated at around 1 64 106 t of which at least 99 is transported in suspension annual total load downstream from the dams is estimated at around 0 45 106 t of which 60 is transported in suspension and the remaining 40 as bedload mean d50 bl in the range of 32 mm total load represents 3 of what was transported at the beginning of the 20th century in the delta plain sediment yield is three to four times lower below the dams a fact that is caused by the trapping of sediment within the reservoirs around 90 in the case of suspended sediment and 100 in the case of bedload as a consequence sediment that is transported downstream from the dams is all entrained from the riverbed and eroded from the banks the sediment deficit causes a mean riverbed incision of 30 mm per year as estimated from bedload measurements and by means of scour chains and painted pebbles located between the lowermost dam and the measuring section 28 km downstream since floods have been reduced on average by 25 but sediment supply from upstream has been reduced to almost nothing the river channel of the lower ebro river will continue exporting sediment both during floods 2000 m3 s mostly bedload and frequent high flows 1000 m3 s to 2000 m3 s making the incision progressive unless restoration steps are taken

seismic wavelet estimation a frequency domain solution to a geophysical noisy input output problem in seismic reflection prospecting for oil and gas a key step is the ability to estimate the seismic wavelet impulse response traveling through the earth such estimation enables filters to be designed to deblur the recorded seismic time series and allows the integration of downhole and surface seismic data for seismic interpretation purposes an appropriate model for the seismic time series is a noisy input noisy output linear model the authors tackle the estimation of the impulse response in the frequency domain by estimating its frequency response function they use a novel approach where multiple coherence analysis is applied to the replicated observed output series to estimate the output signal to noise ratio snr at each frequency this combined with an estimate of the ordinary coherence between observed input and observed output and with the spectrum of the observed input and cross spectrum of the observed input and output enables estimation of the frequency response function the methodology is seen to work well on real and synthetic data

critical conditions for particle motion in coarse bed materials of nonuniform size distribution initiation of particle motion in a bed material of nonuniform size distribution may be quantified by qci qcr di dr b where qci is the critical unit discharge at which particle size di enters motion qcr is the critical condition for a reference size dr unaffected by the hiding exposure effects associated with nonuniform size distributions i and r refer to percentiles of the distribution and b varies from 0 equal mobility in entrainment of all particle sizes to 1 5 2 5 full size selective transport currently there is no generally accepted method for predicting the value of b flume and field data are therefore combined to investigate the above relationship thirty seven sets of flume data quantify the relationship between critical unit discharge and particle size for bed materials with uniform size distributions used here to approximate full size selective transport field data quantify the relationship for bed materials of nonuniform size distribution at 24 sites with b ranging from 0 15 to 1 3 intersection of the two relationships clearly demonstrates the hiding exposure effect in some but not all cases dr is close to the median size d50 the exponent has two clusters of values b 1 for sites subject to episodic rain fed floods and data collected by bedload pit trap and tracers and b 1 sites with relatively infrequent bedload transport where particle embedding and consolidation could reduce the mobility of coarser particles and for b 0 7 a looser bed structure with frequent transport events allowing hiding exposure and size selection effects to achieve their balance as yet there is no firm evidence for such a dependency on bed structure but variations in b could potentially be caused by factors outside those determining equal mobility or size selection but appearing to affect b in the same way

a field comparison of three pressure difference bedload samplers abstract the movement of bedload over a cross section is often sampled using a pressure difference bedload sampler such as the helley smith whereas several types are in use no one device has gained universal acceptance as the standard for use in all types of streams moreover evidence suggests that similar devices may collect substantially different amounts of bedload because of only slight modifications in design in this study sample weights collected by three types of pressure difference samplers are compared to determine whether differences are statistically significant or whether sampler performance is so irregular and overlapping that one might regard them as being the same the results confirm that the weights of samples collected by the devices are significantly different generally the us blh 84 collected less material the sheetmetal helley smith collected more material and the original helley smith was intermediate these tendencies were consistent at two sites where bedload was measured the implication of these results is that measured transport rates will vary depending on the sampler used and therefore they are not directly comparable without some mode of calibration to place this finding in a larger context sediment rating curves determined from weights of samples and measurements of flow were integrated over available flow records and used to estimate annual yield three estimates of annual yield one for each device were then compared with measures of annual accumulation from a weir pond below one of the collection sites the results indicate that despite differences between the devices data obtained with pressure difference samplers estimated annual accumulations of sediment reasonably well predicted accumulations were within 40 50 of the measured yield for two samplers whereas the third sampler predicted within 80

bedload transport in a river confluence abstract the confluence of the regulated tolten river and its tributary the unregulated allipen south of chile has proved dynamic in the last decade daily bedload measurements with a helley smith sampler bed surveys and grain size distributions of the two rivers are obtained from a field campaign that lasts 3 months in high flow season the goals are to quantify total bedload and to understand the balance between tributary and main river and the bedload distribution in space and texture the bedload transport varies 200 fold with a maximum of 5000 t day the discharge varies five fold with a maximum of 900 m 3 s two thirds of the total bedload volume are transported through the deeper area of the cross section and gravel is predominant 64 average bedload volumes in the confluence seem unbalanced in favour of the tributary main river bedload transport is predominantly at below capacity conditions while the tributary bedload transport is at capacity conditions this is deemed the main reason of inaccuracy of the bedload predictors the roles of entrainment into suspension helical flow partial transport and mobile armour are discussed

bed material transport estimate in large gravel bed rivers using the virtual velocity approach this paper reports on a first attempt of using the virtual velocity approach to assess sediment mobility and transport in two wide and complex gravel bed rivers of northern italy displacement length and virtual velocity of spray painted tracers were measured in the field also the thickness of the sediment active layer during floods was measured using scour chains and post flood morphological changes as documented by repeated survey of channel cross sections the effects of eight and seven floods were studied on the tagliamento and brenta rivers where 259 and 277 spray painted areas were surveyed respectively in the tagliamento river 36 of the spray painted areas experienced partial transport whereas in the brenta river this accounted for 20 whereas full removal gravel deposition was observed on 37 and 26 of these areas on the tagliamento and brenta rivers respectively the mean displacement length of particles the thickness of the active layer and the extent of partial transport are well correlated with the dimensionless shear stress the virtual velocity approach allowed calculation of bed material transport over a wide range of flood magnitudes annual coarse sediment transport was calculated up to 150 for the tagliamento and 30 103 m3 yr 1 for the brenta the outcomes of this work highlight the relevance of partial transport condition as it could represent more than 70 of the total bed material transported during low magnitude floods and up to 40 for near bankfull events results confirm that bed material load tends to be overestimated by traditional formulas copyright 2016 john wiley sons ltd

the influence of lee sediment behind large bed elements on bedload transport rates in supply limited channels a coarse surface layer can help to limit bedload transport rates in channels with cobble and gravel beds in these systems periodic boulder sized clasts often exist with small deposits of fine material in the lee of these large bed elements a combined field and flume study was conducted to investigate the potential impact of lee deposits with distinctly finer sediment sizes behind boulders on bedload transport rates detailed sediment characterizations were performed on surface subsurface and lee sediments in two coarse bedded connecticut channels bedload measurements also were conducted in a series of flows that approached the bankfull level in these two systems to determine transport rates and the size distribution of bedload material a 6 m long 0 5 m wide flume was used to model these systems with fine sediment passing over a fixed bed of sediment particles with uniform sized large bed elements sediment distributions of the lee deposits in the two connecticut channels indicate that lee deposits may be produced from winnowing of sediments from the surface layer lee deposits also exhibit sediment distributions similar to bedload sediment distributions from low to near bankfull flow in one of the two channels bedload sediments in the second channel were finer than lee deposits presumably from selective entrainment of fines flume experiments demonstrate that bedload transport rates are lower for periods of steady flow relative to periods that include either an increase or decrease in discharge the results show that lee sediments establish a metastable deposit behind each obstruction for a given discharge either increases or decreases in discharge disrupt this temporary stability and increase sediment delivery to the main flow the study suggests that the influence of the rate of change in discharge may be as important as the absolute magnitude of discharge on sediment transport rates at moderate and low discharges in sediment limited systems with large bed elements

forced regressions in a large wave and storm dominated anoxic lake rhaetian sinemurian kap stewart formation east greenland during rhaetian sinemurian time a large wave and storm dominated lake was situated in the jameson land basin east greenland lake deposits consist of alternating black unfossiliferous mudstones and sheet sandstones anoxic conditions dominated at the lake bottom during deposition of the muds and the water column was probably stratified the sandstones were deposited by progradation of wave and storm dominated deltas in a water depth of less than 15 m sequence stratigraphic interpretation suggests that the mudstones were deposited in periods of rising and very high stands of lake level whereas progradation of the deltaic sheet sandstones took place during forced regressions caused by significant falls the lake thus underwent a large number of fairly high amplitude changes in level probably caused by climatic fluctuations the high order cycles can be grouped into several long period cycles that show the same number of major fluctuations as published eustatic sea level curves this similarity suggests a causal link between eustasy and long period variations in the lake the kap stewart formation represents one of the few ancient examples of a large wave and storm dominated lake and it is probably the first documented case of abundant well developed lacustrine forced regressions

lithofacies and fluvial lacustrine environments of the palaeogene sevkhuul and ergil members ergiliin zoo formation south gobi mongolia the clastic sequence of the ergiliin zoo formation stretches along the mongolian chinese border in the southern gobi desert mongolia its members sevkhuul ergil exposed in the erdene sum region are well known for their vertebrate remains of late eocene and oligocene age based upon field work the continental red beds were subdivided into four units described as i prodelta mud sand flat ii delta front iii delta plain and iv calcretes all sub environments are in a fluvial lacustrine setting electronmicroprobe analysis in addition to conventional thin section examination was applied to shed some light on the complex mineral association made up of light minerals quartz plagioclase ternary feldspar orthoclase smectite illite rare palygorskite heavy minerals almandine pyrope solid solution series zoisite epidote s s s and abundant goethite and carbonate minerals calcite dolomite igneous rocks being exposed in the source area have contributed to the formation of carbonate minerals and mg bearing sheet silicates during diagenesis higher up on the delta plain transitional between distal alluvial and deltaic deposits fluids emerged from the distal alluvial fluvial deposits and formed calcareous duricrusts drawing conclusions from the rock colour the mineral assemblage and the palaeoecological data the climatic conditions may be described as alternating wet and dry seasons closely resembling those conditions of a modern savannah

lacustrine sedimentation in the diapir controlled miocene bicorb basin eastern spain abstract the miocene bicorb basin is a small elongated basin developed by normal faulting of a thick jurassic cretaceous carbonate succession and subsequent diapirism of upper triassic mudstones and evaporites the basin fill comprises a sequence over 650 m thick formed by two units the lower alluvial unit consists of a complex alternation of conglomerates sandstones mudstones and minor lacustrine limestones the upper unit comprises marginal alluvial and lacustrine deposits in which seven lacustrine facies associations have been distinguished the inner lacustrine deposits comprise mudstones and carbonates with minor evaporitic deposits at the northeast and southwest basin edges alluvial inputs led to the development of delta and fan delta environments where sandstone and conglomerate deposits dominate the latter stages of the lake evolution are represented by an expansive thick limestone sequence which close to the nw fault bounded margin pass laterally to breccias the hierarchical arrangement of the upper unit shows five different orders of sequences the first order sequence defines a major vertical trend of lake expansion whereas three second order sequences are linked to major flooding expansion episodes all these sequences are related to the tectonic evolution of the diapir metre scale third and fourth order sequences and fifth order sequences which consist of finely laminated rhythmite deposits probably record climatically forced processes the diapir graben system evolution and the climatic variations have exerted major controls on the sequential arrangement and evolution of the lacustrine system both factors have also strongly influenced the changes in the gastropod assemblages

the hydrological setting occurrence and significance of gypsum in late quaternary salt lakes in south australia well exposed often laminated gypsum sequences occur in many quarternary salt lakes in southern south australia the gypsum in the salt lakes is classified by increasing grain size into gypsite gypsarenite and selenite the salt lakes are classified by age and hydrological setting into coastal salinas which are holocene sea water fed groundwater lakes and continental playas which are late pleistocene endorheic basins a study of the relationships between coastal salina hydrology and the associated gypsum deposition has shown the different types of gypsum form under distinct hydrological regimes as the hydrology above a coastal salina depositional surface changes through time so does the type of gypsum deposited application of a gypsum depositional model derived from a study of the coastal salina gypsum to those portions of a continental playa gypsum unit where deposition is no longer occurring confirms the applicability of the model to non salina gypsum deposits

the trouble with shear stress abstract predicted bedload fluxes often have large errors partly because calculations usually do not include spatial and temporal flow variability sediment motion is driven by a temporal distribution of applied fluid forces which are often simplified into time averaged flow velocities or shear stresses in sediment transport equations spatial variations in these flow parameters are also often neglected given the nonlinearities in the relation between flow and sediment flux the reach averaged sediment flux calculated with an average velocity or shear stress will not necessarily equal the measured spatially averaged bedload flux such spatial and temporal flow variations are ignored with the commonly used reach averaged shear stress ds that is a function of the flow depth and channel slope to demonstrate the uncertainties with using reach averaged shear stresses and even local shear stresses to predict bedload transport rates we have three goals first we outline the derivations and assumptions involved with commonly used estimates of shear stress second we summarize the literature on the uncertainties involved with using shear stress and other space and time averaged flow parameters to predict sediment flux third we use a new data set from experiments to add further support to a growing body of literature that suggests ds may not be linked to the mechanics of bedload transport we show considerable uncertainties exist in estimating a reach averaged shear stress by comparing ds and near bed shear stresses calculated from velocity profiles reynolds stresses and local turbulence for example ds was systematically greater than these near bed stresses even for experiments without large bed roughness we also find that correlations between local time averaged sediment fluxes and local reynolds stresses or turbulence intensities are relatively poor the near bed time averaged local flow velocity has the strongest relation with the time averaged local bedload flux because it is closely related to the forces that actually drive sediment transport however sediment transport rates in individual experiments could still vary by orders of magnitude for a given value of this flow velocity suggesting that additional work is needed to identity a parameter or distributions of parameters that will best predict sediment fluxes

sediment entrainment and depletion from patches of fine material in a gravel bed river characteristics at shear stresses ranging from 5 to 60 n m 2 experiments demonstrate that patches of fine sediment control both the intensity and duration of bed load under hydraulic conditions characteristic of the early stages of floods the experiments allow quantifying bed load at the entrainment threshold providing the first empirical evidence that marginal bed load transport can be attributed to the mobilization of sediments from patches bed load transport was recorded consistently once shear stress exceeded 5n m 2 the experiments produced low bed load rates 6 g sm depletion of material in the patches occurred rapidly with bed load rates and particle sizes decreasing after only 5 minutes combining flume and helley smith data for the study reach a breakpoint in the relation between shear stress and bed load rate was calculated to be around 30 n m 2 this represents the transition between bed load transport phases below the breakpoint transport occurs at a low rate and is composed predominantly of fine sediment from patches but above it much higher rates occur from across the reach as a whole hydraulic conditions at the threshold are those which occur during small frequent floods 25 bankfull flow equaled or exceeded 15 of time this indicates that sediment entrainment from patches of fine material is a frequent process and the threshold change between bed load phases occurs regularly

an investigation of the spectral properties of primary reflection coefficients this paper investigates the form of the nonwhiteness found in the reflection coefficients from a wide variety of rock sequences around the world in all but one case densities are taken as constant due to the paucity of suitable density data the reflection sequences are pseudo white only above a corner frequency below which their power spectrum falls away according to a power law f where is between 0 5 and 1 5 this spectrum can be adequately modelled in practice very simply with an arma 1 1 process which acts on a white innovation sequence the corollary of this is that before wavelet estimation methods are applied all of which except those based on synthetic seismograms presuppose white reflection sequences or deconvolution filters estimated seismic traces should be filtered with the inverse of this process interestingly the estimated arma processes group themselves into two clearly differentiated categories having very different indices of predictability or strictly indices of linear determinism the two categories apparently correlate precisely with two kinds of sedimentation one which consists largely of sequences of rocks with repeating properties called repetitive in this paper but perhaps loosely describable as cyclic and the other which is randomly bedded with no apparent pattern of components the former has indices of predictability which are two to four times as great as those of the latter another probably related property is that for the repetitive sequences tends to be greater than that for non repetitive rock columns the observed power spectra are shown to be consistent with a simple model for the logarithm of acoustic impedance consisting of a mixture of processes where the distribution of time scale parameters is reciprocal detailed effects of block averaging and sampling the logs are shown to depend on the type of sequence under examination

calcite precipitation in lake constance chemical equilibrium sedimentation and nucleation by algae1 seasonal shifts in calcium carbonate solution equilibria in the limnetic zone of lake constance were documented between 1981 and 1983 except during mixing times lake water was supersaturated with respect to calcite epilimnetic supersaturation maxima were closely related to changes in ph sedimentation of calcium from the lower boundary of the euphotic zone to the lake bottom was also assessed the daily sedimentation flux for calcium during the season varied over three orders of magnitude differences in the calcium content of sediments trapped at various depths were insignificant sedimentation rates of titanium were used as tracers for the fluxes of calcium bound on allochthonous elastic material lacustrine calcite precipitation 39 49 of the total sedimentation rate was obtained by subtracting fluxes of allochthonous ca from the rates of total ca sedimentation calcium supersaturation maxima were not in phase seasonally with maximum fluxes of autochthonous ca instead calcite precipitation was associated with the occurrence of stephanodiscus hantzschii fragilaria crotonensis asterionella formosa chlorella sp pandorina morum and mougeotia thylespora indicating that calcite formation was triggered by heterogeneous nucleation induced by certain algal species autochthonous formation and subsequent precipitation of calcium carbonate is an important process in the carbon and calcium cycling in many hard waters through coprecipitation calcium carbonates affect nutrient budgets rossmann 1980 rossknecht 1980 murphy et al 1983 and by adsorption they remove dissolved organic carbon doc from the water suess 1970 chave and suess 1970 otsuki and wetzel 1972 hence several studies have focused on the formation reactions settling processes and deposition of caco in lakes cf

late miocene to plio pleistocene fluvio lacustrine system in the karacasu basin sw anatolia turkey depositional paleogeographic and paleoclimatic implications abstract the sedimentary record of the late cenozoic karacasu basin a long lived continental half graben from southwestern turkey is characterized by siliciclastic and carbonate deposits sedimentation was controlled by an active nw se trending major normal fault along the basin s southern margin and by climatically induced lake level changes detailed facies analysis subdivides the entire neogene quaternary basin fill into three distinct litostratigraphic units representing paleogeographic changes and sedimentation patterns throughout the basin evolution sedimentation commenced in the late miocene with the deposition of proximal medial alluvial fan and fluvial facies damdere formation fa1 at this stage alluvial fans developed in elevated areas to the south prograding towards the basin center at the beginning of the pliocene fresh to slightly alkaline shallow lake deposits fa2a of the karacaoren formation formed the lake became open and meromictic conditions developed fa2b pollen data from the fa2b facies show that climate was arid to humid climate probably changed cyclically through time producing alternation of artemisia steppe cold and dry periods and more forested vegetation warm and wet the open lake facies passes upwards into lake margin facies fa2c but it was still dominated by alkaline to slightly saline lake conditions sedimentation was almost continuous from the late miocene to pleistocene in the early quaternary the basin was dissected by the re activation of basin bounding faults the unconformable base of the overlying quaternary deposits karacasu formation fa3 reflected the basin s transformation from a half graben into a full graben system oxygen isotope data from carbonates show an alternation of humid climatic periods when freshwater settings predominated and semiarid arid periods in which the basin hosted alkaline and saline water lakes neotectonic activity has rejuvenated many of the basin bounding faults causing development of talus aprons and local alluvial fans the basin was progressively incised by modern rivers that have largely smoothed out the topographic relief of the graben margins

effect of flood basalt stratigraphy on the phase of seismic waveforms recorded offshore faroe islands abstractthe generation of short period multiples between highly heterogeneous layers of basalt flows can strongly alter transmitted seismic wavefields these layers filter and modify penetrating waves producing apparent attenuation and phase changes in the observed waveforms we investigated the waveform and apparent phase changes of the primary seismic signal using mainly the maximum kurtosis approach we compared the seismic recordings from two short offset vertical seismic profiles vsps with synthetic seismograms generated from sonic logs in the same wells and we found that short period multiples cause a rapid broadening of the primary arrivals and strong apparent phase changes within a short depth interval below the top of the basalt flows relatively large uncertainties were associated with estimating constant phase shifts of the seismic arrivals within the topmost 250 m of the basalt sequences where complex scattering occurred within this interval of the brugdan i well a phase only compensat

the cretaceous uhangri formation sw korea lacustrine margin facies the uhangri formation forms part of the cretaceous sedimentary sequence deposited in a series of inland basins in the south western korean peninsula it comprises an approximately 400 m thick epiclastic sequence of conglomerate gravelly sandstone cherty mudstone and black shale the entire sequence can be represented by 16 distinctive sedimentary facies organized into four facies associations facies association i is characterized by thick homogeneous brownish siltstone wedge shaped disorganized conglomerate and thinly interlayered gravelly sandstone units the siltstone units were formed by large floods submerging the alluvial fan fringe floodplain whereas the conglomerate and gravelly sandstone units were deposited by sheetfloods and debris flows facies association ii consists of stratified conglomerate gravelly sandstone laminated sandstone and sandstone siltstone couplets which form fining upward cycles some facies units are low angle trough cross bedded and show broad channel geometries this association represents subaqueous delta lobes fed by high and low concentration turbidity currents in the distal delta realm facies association iii is characterized by wedged conglomerate and gravelly sandstone facies with interfingered massive sandstone bounded by scoured bases it represents a delta front where distributary channels and mouth bars are dominant facies association iv consists of laterally continuous sequence of laminated black shale crudely stratified sandstone and convoluted sandstone cherty mudstone this facies association is suggestive of depositional processes controlled by chemical equilibrium resulting from an interaction between density inflows and lake water the cherty mudstone resulted from inorganic precipitation from siliceous solution provided by acidic volcanism the uhangri sequence generally shows a fining upward trend with a transition from alluvial fan fringe coarse grained subaqueous delta to shallow lake the retrogradation was probably due to continuous subsidence related to continental rifting in the oblique slip mobile zone

estimating bedload transport in a large sand gravel bed river from direct sampling dune tracking and empirical formulas three methods used to estimate river bedload discharges were compared in a large sand gravel bed river the unit and total bedload transport rates estimated by sediment sampling dune tracking method and the equations of van rijn and meyer peter and muller were compared the analysis was based on a large data set obtained from field surveys that combined sediment sampling acoustic doppler profiler adp measurements and multibeam echosoundings of the middle reach of the river loire france for contrasting flow conditions ranging from low flows to 2 year floods for transport stages between 2 and 6 i e between the annual mean discharge and the discharge for a 2 year flood the tested equations predicted fairly well the unit and total bedload discharges and roughly estimated the temporal variability of the bedload during floods for these transport conditions the best agreement with the sediment sampling measurements was observed with the van rijn formula for lower flow conditions the tested formulas provide lower estimates than those sampled to improve the accuracy of the equations for low flows potential solutions include integrating near bed turbulences and non uniformity of bed particles into the models the ability of the formulas to predict the temporal variability of the bedload can be improved by using the bedform roughness to adjust the estimates the bedload transport rates calculated with dune tracking method are lower than the fluxes sampled because a substantial fraction of the bedload does not participate to the dune migration finally a first rating curve that was implemented for the river loire estimates the annual bedload discharge for 2010 to be 480 000 t

temporal variations in bedload transport rates associated with the migration of bedforms temporal variations in bedload transport rates that occur at a variety of timescales even under steady flow conditions are accepted as an inherent component of the bedload transport process rarely however has the cause of such variations been explained clearly we consider three data sets obtained from laboratory experiments that refer to measurements of bedload transport made with continuously recording bedload traps each data set is characterized by a predominant low frequency oscillation on which additional higher frequency oscillations generally are superimposed the period of these oscillations as isolated through the use of spectral analysts ranged between 0 47 and 168 minutes and was associated unequivocally with the migration of bedforms such as ripples dunes and bars the extent to which such oscillatory behaviour may be recognized in a data set depends on the duration of sampling and the length of the sampling time with respect to the period of a given bedform several theoretical probability distribution functions have been developed to describe the frequency distributions of relative bedload transport rates that are associated with the migration of bedforms einstein 1937b hamamori 1962 carey and hubbell 1986 these distribution functions were derived without reference to a sampling interval we present a modification of hamamori s 1962 probability distribution function generated by monte carlo simulation which permits one to specify the sampling interval in relation to the length of a bedform comparisons between the simulated and observed frequency distributions that were undertaken on the basis of the data described herein are good significant at the 90 per cent confidence level finally the implications that temporal variability which is associated with the migration of bedforms have for the accurate determination of bedload transport rates are considered

bed load bias comparison of measurements obtained using two 76 and 152 mm helley smith samplers in a gravel bed river 1 we assess how the size of the helley smith hs bed load sampler nozzle affects the accuracy of bed load sampling semitheoretical considerations show that the larger grains resident on the streambed can influence the sample either by blocking the sampler entrance or by causing the sampler to rest in a perched position probabilities for interference can be derived from the distribution of grain sizes but they do not capture the actual complexity of the influence of the bed on sampler performance we therefore make an empirical comparison of sediment trapped by hs samplers with 76 and 152 mm intakes during floods in the gravel bed lower ebro river most bed load rates appeared higher when sampled with the hs152 the largest clasts collected by the hs76 also tend to be smaller than those obtained with the hs152 at the same flow analyzing paired bed load samples we find the probability of a bed load sample collected with the hs152 to be biased is around 43 in the conditions of the present study whereas 65 of samples were biased when obtained with the hs76 the analysis emphasizes the influence of bed material texture over sampler performance and demonstrates that the use of samplers with intake size much larger than bed grain size i e 5d will increase the accuracy of bed load grain size distributions and the precision of annual load estimates in gravel bed rivers

magnetotelluric characterization of a salt diapir a case study on bicorb quesa diapir prebetic zone se spain abstract the availability of geophysical data to determine the geometry at depth of a salt diapir and its surrounding structure is essential because of the complexity and changing geometry of these structures for this purpose potential field methods are commonly the first steps in subsurface exploration whereas seismic techniques are applied in later stages however the magnetotelluric method mt may fill the gap between the precision and the time that these two methods entail to prove the usefulness of the mt method it has been applied to the bicorb quesa diapir this diapir is composed of evaporitic rocks piercing an overburden of carbonate rocks providing a wide and contrasting range of electrical resistivity values in this situation the mt method may provide a coherent and realistic image of the subsurface the application of the mt method has allowed us to 1 recognize a basement fault with a vertical throw of 1000 m 2 elucidate the shape of the diapir which is asymmetrical with a north wall vertical and south wall dipping southwards and 3 determine that all of the late triassic salt is concentrated in the diapir core supplementary material original curves and the model adjustments are available at http www geolsoc org uk sup18386

hydrology and bedload transport relationships for sand bed streams in the ngarradj creek catchment northern australia summary rainfall discharge and bedload were measured at three gauging stations east tributary upper swift creek and swift creek in the ngarradj creek catchment at jabiluka northern territory australia hand held pressure difference helley smith bedload samplers were used to measure bedload fluxes for the 1998 1999 1999 2000 2000 2001 and 2001 2002 wet seasons rainfall is strongly seasonal over the ngarradj creek catchment being concentrated in the wet season between november and april mean annual point rainfall between 1998 and 2007 for the water year september to august inclusive varied over the ngarradj creek catchment from 1731 98 mm se to 1754 116 mm between 190 and 440 mm of rainfall are required before streamflow commences in december in most years streamflow persists until at least april mean annual runoff as a percentage of mean annual rainfall decreases slightly with increasing catchment area bedload ratings were calculated for four data sets significant bedload ratings were defined as those that were not only statistically significant 0 05 but also explained at least 0 60 of the variance in bedload flux for the three stations twenty three bedload ratings complied with the above criteria sixteen equations were accepted for east tributary four bedload ratings were accepted for upper swift creek and three bedload ratings were accepted for swift creek significant bedload ratings were established between bedload flux and discharge unit bedload flux and discharge transport rate of unsuspended bedload by immersed weight per unit width and time and both unit and excess unit stream power and finally adjusted submersed bedload weight and both unit and excess unit stream power for raw and log10 transformed data censored data sets were compiled for upper swift creek and swift creek to include only bedload fluxes measured when there was no apparent scour or fill so that there were no changes in sand supply from the catchment i e equilibrium conditions bedload sediments are similar at all sites there is little difference in grain size statistics between wet season bedload and dry season bed material the differences which were significant suggest that most of the bed material is transported as bedload during the wet season size selective transport occurs at all three gauging stations with bedload being better sorted than bed material and the coarsest fraction cobble gravel is mobile only during extreme events

sediment transport in a highly regulated fluvial system during two consecutive floods lower ebro river ne iberian peninsula the transfer of sediment through a highly regulated large fluvial system lower ebro river was analysed during two consecutive floods by means of sediment sampling suspended sediment and bedload transport were measured upstream and downstream of large reservoirs the dams substantially altered flood timing particularly the peaks which were advanced downstream from the dams for flood control purposes the suspended sediment yield upstream from the dams was 1 700 000 tonnes which represented nearly 99 per cent of the total solid yield the mean concentrations were close to 0 5 g l 1 the sediment yield downstream from the dams was an order of magnitude lower 173 000 tonnes showing a mean concentration of 0 05 g l 1 the dams captured up to 95 per cent of the fine sediment carried in suspension in the river channel preventing it from reaching the lowermost reaches of the river and the delta plain total bedload transport upstream from the dams was estimated to be about 25 000 tonnes only 1 5 per cent of the total load the median bedload rate was 100 gms 1 below the dams the river carried 178 000 tonnes around 51 per cent of the total load at a mean rate of 250 g ms 1 the results of sediment transport upstream and downstream from the large dams illustrate the magnitude of the sediment deficit in the lower ebro river the river mobilized a total of 350 000 tonnes in the downstream reaches which were not replaced by sediment from upstream therefore sediment was necessarily entrained from the riverbed and channel banks causing a mean incision of 33 mm over the 27 km long study reach altogether a significant step towards the long term degradation of the lower ebro river copyright 2005 john wiley sons ltd

principles and application of maximum kurtosis phase estimation1 methods of minimum entropy deconvolution med try to take advantage of the non gaussian distribution of primary reflectivities in the design of deconvolution operators of these wiggins 1978 original method performs as well as any in practice however we present examples to show that it does not provide a reliable means of deconvolving seismic data its operators are not stable and instead of whitening the data they often band pass filter it severely the method could be more appropriately called maximum kurtosis deconvolution since the varimax norm it employs is really an estimate of kurtosis its poor performance is explained in terms of the relation between the kurtosis of a noisy band limited seismic trace and the kurtosis of the underlying reflectivity sequence and between the estimation errors in a maximum kurtosis operator and the data and design parameters the scheme put forward by fourmann in 1984 whereby the data are corrected by the phase rotation that maximizes their kurtosis is a more practical method this preserves the main attraction of med its potential for phase control and leaves trace whitening and noise control to proven conventional methods the correction can be determined without actually applying a whole series of phase shifts to the data the application of the method is illustrated by means of practical and synthetic examples and summarized by rules derived from theory in particular the signal dominated bandwidth must exceed a threshold for the method to work at all and estimation of the phase correction requires a considerable amount of data kurtosis can estimate phase better than other norms that are misleadingly declared to be more efficient by theory based on full band noise free data

sedimentology of coarse grained alluvial fans in the markham valley papua new guinea abstract in alluvial sediment sequences recognition of a hierarchy of bounding surfaces and the shapes and associated lithofacies of the sediment bodies they define provide an appropriate framework for understanding associations among depositional forms the processes responsible for them and their controls on system development this methodology architectural element analysis integrates principles from geomorphology and sedimentology miall 1985 1988 it is used here to analyse the evolution of the modern umi fan and the alluvial fan part of the pleistocene leron formation in the markham valley papua new guinea a series of terraces has developed as the umi river has incised into its fan detailed stratigraphic analysis of the lowest terrace in exposures up to 25 m high and kilometres long reveals that the fan is dominated by sheetflood deposits with minimal preservation of either debris flow or hyperconcentrated flood flow sediments channel fill elements make up a larger proportion of exposures in the proximal fan than elsewhere while 95 of distal fan exposures are composed of sheetflood sequences these depositional features likely result from massive sediment dispersal associated with the rapidly uplifting upland terrain abundant sediment availability and flashy discharge regime channel fill units along with slope related deposits from debris and hyperconcentrated flood flows are only likely to be preserved in the trench backfilling phase following fan entrenchment reworking of deposits plays a dominant role in preservation of sheetflood deposits at the expense of slope related deposits an hierarchical framework of lithosomes is developed which characterizes various scales and bounding surfaces of depositional units which make up the umi fan cf miall 1988 decelles et al 1991 smaller elements observed in terrace exposures are described as first to fourth order lithosomes they reflect geomorphic processes which are evident in and adjacent to the modern umi river deposits which infill the trench are interpreted as a fifth order lithosome constrained by trench geometry proximal distal relationships are remarkably similar in the umi fan and leron formation fan sequences in both instances debris flow deposits are seldom observed the largest sixth and seventh order lithosomes which were deposited within a time frame of approximately one hundred thousand years are interpreted by analysis of the leron formation in relation to its tectonic setting the umi and pleistocene leron formation fans exemplify fan development in a post collisional molasse basin under a tropical monsoonal climate carbonate concretions observed in distal fan facies may provide a possible diagnostic feature of these tropical savanna fans

holocene sedimentology of hypersaline lake urmia northwestern iran abstract a limnogeological expedition examined the sedimentary record of lake urmia one of the world s largest saline lakes located in a tectonically active arid intermontane plateau in northwestern iran near the cradle of western civilization lake urmia resembles the great salt lake u s a in many respects of morphology water chemistry and sediments the present lake area is about 5000 km 2 shallow 8 12 m and a perennial sodium chloride sulfate system 22 salts high resolution 3 5 khz seismic profiles show morphological relicts from a desiccation playa phase buried below only a few meters of sediments from lacustral phases in places around the deeper areas the lake floor is not smooth but covered with mounds aligned in prevailing current directions these are erosional relicts rather than bioherms sediments comprise aragonite chemical precipitates fecal pellet sands detrital clayey muds thin aragonite crusts oolites various gypsum types and occurrences of dolomite in peripheral areas organic matter characteristic of the present shorelines is not preserved at depth in basinal areas piston cores up to 6 m long penetrated a holocene sequence of hypersaline facies with laminated aragonite fecal pellet muds and bottomed in a playa mudflat facies with central gypsiferous muds and marginal terrigenous to dolomitic muds preliminary radiocarbon and pollen analyses suggest a playa stage prior to 9000 yr b p with saline lake deposition in a cool arid climate from 9000 to 7500 yr b p higher energy facies prevailed in a shallow saline lake and since then present day saline environments have persisted with evidence of numerous second order water level fluctuations the preliminary results suggest a lake system out of phase with north african and some other middle eastern lakes

facies related diagenetic alteration in lacustrine deltaic red beds of the paleogene ergeliin zoo formation erdene sum area s gobi mongolia the late eocene ergeliin zoo formation mongolia was subdivided into four facies associations stratigraphic units which are characterized by various carbonate minerals 1 mud sand flat low fe dolomite high mg calcite 11 delta front high mn dolomite low mg calcite 111 delta plain high mn calcite low mg and moderate fe calcite iv calcretes high mg calcite besides carbonate minerals prevailing among the cement minerals some sheet silicates ca smectite palygorskite illite apatite and fe oxide hydroxides occur in the siliciclastics of these lacustrine deltaic red beds the prodelta mud sand flat deposits unit 1 were dolomitized and cemented by high mg calcite during evaporative pumping at times of low lake stand under redox conditions greater than 0 and intrastratal solutions of strong alkalinity manganoan dolomite is fairly widespread in the delta front sediments unit 11 the mn content of which is likely to have been derived from decomposition of vertebrate remains the mn fe ratio in the carbonate minerals was controlled by the redox conditions and the shallow burial depth in the porous delta front sediments eh values around zero and ph values slightly above 7 occurred as a result of basinward fluid movements high mn dolomite high fe dolomite low mg calcite fluid movement was locally impeded by finer grained delta plain deposits unit iii intertonguing with arenaceous aquifers low mg moderate fe calcite high mn calcite higher up on the delta plain with deposits laid down in an environment transitional between distal alluvial and deltaic unit iv closed lake basin conditions reappeared as fluids emerged from the distal alluvial fluvial deposits or were driven by capillary force to ascend and form calcretes abundant in mg bearing calcite the climatic conditions in the erdene sum area mongolia are likely to have been semi and transitional into arid c 2005 elsevier b v all rights reserved

sediment transporting flows in headwater streams the equilibrium alluvial stream channel has a geometry that allows it to pass the water and sediment supplied from the watershed at the same time the equilibrium alluvial channel is built and maintained by the flows and sediment delivered to it a prerequisite for understanding the creation of the equilibrium channel is an understanding of the sediment conveyance and competence of the flows the channel receives this study describes the bed load transport regime as it is linked to hydrology and geomorphology in 23 headwater gravel bed streams in snowmelt dominated parts of central and northern idaho at sites drainage areas range from 1 29 to 381 km 2 stream gradients range from 0 0042 to 0 0747 and median bed surface particle sizes range from 4 to 207 mm stream architecture includes riffle pool planar and step pool beds the bed load is much finer than the surface and subsurface material suggesting selective transport of the finer sizes nonetheless the majority of the load is sand at all flow discharges progressively coarser sediment was collected as flow discharge increased and painted rock experiments documented the transport of coarser particles at higher discharges the supply of sediment to the streams appears limited as indicated by observed clockwise hysteresis in bed load transport rates during each spring snowmelt and by the coarse surface armor observed at sites flows above bankfull discharge move 37 of the bed load whereas flows between mean annual discharge and bankfull move 57 of the bed load the bed load effective discharge has a recurrence interval that averages 1 4 yr and the magnitude of effective discharge averages 80 of bankfull discharge the recurrence interval of bankfull discharge averages 2 0 yr the ratio of effective discharge to bankfull discharge is independent of basin size grain size and gradient although the ratio increases with the relative magnitude of large infrequent events

the influence of basement structure on the evolution of the bicorb quesa diapir eastern betics iberian peninsula contractive thin skinned deformation above a pre existing extensional basement fault on the basis of an analysis of structural surface data in addition to previously available and new magnetotelluric data it was possible to reconstruct the evolution of bicorb quesa diapir this was initiated as a reactive diapir in relation to a basement fault the reactive diapir was rejuvenated by a thin skinned compression during the paleogene and rose during an extensional early middle miocene phase later in the middle miocene the diapir was squeezed and then in the late miocene was extensionally reactivated the current reconstruction allows us to analyse a diapir affected by a thin skinned contractional deformation located on top of a pre existing basement fault our study highlights the role played by the geometric relationship between the propagation direction of the cover deformation and the basement fault

perspectives on the sequence stratigraphy of continental strata this report is the result of a working group on continental sequence stratigraphy that was set up at the 1991 nuna conference in banff canada to date sequence stratigraphic concepts have been applied mainly to the marine realm but unconformity bounded units have long been recognized in nonmarine strata successful application of sequence stratigraphic concepts to continental strata requires careful consideration of controls on base level and sediment supply as with shallow marine environments relative sea level can be considered as the stratigraphic as well as the geomorphic base level for coastal nonmarine settings farther inland stratigraphic base level which determines accommodation space is more complex and takes various forms such as the graded profile for fluvial strata groundwater tables for some eolian strata and lake level for some intermontane sediments sediment supply is also generally a more complex variable for nonmarine environments than in the marine realm because of the proximity to the source area the influence of climate and tectonism on sediment supply can clearly be seen in many continental sediments the fact that the major controls of climate tectonism and eustasy are somewhat interdependent and that a change in one parameter will most likely be reflected in others is also more readily apparent in continental strata although in its infancy sequence stratigraphic concepts have been applied to a wide variety of continental settings in attempts to explain variations in facies architecture of particular interest are studies that have linked fluvial architecture on coastal plains to variations in relative sea level as indicated by coeval marine strata and studies of lacustrine environments that show marked variation in facies between highstand and lowstand deposits the application of sequence stratigraphy to continental strata will likely result in the development of better correlation techniques and models that better predict the location and nature of fluvial and eolian reservoirs

primary and diagenetic carbonates in the anoxic sediments of lake bosumtwi ghana cores of organic rich muds from the tropical meteorite crater lake bosumtwi ghana contain laminae of authigenic calcite polyhedra and aragonite needles as well as scattered diagenetic calcite mg calcite spherulites and aggregates of dolomite crystals their respective origins are traced by analyses of oxygen and carbon stable isotopes anoxic dolomite and mg calcite formed in pore waters reflecting highest degrees of evaporative concentration and high rates of methanogenesis carbon dioxide reduction must have been the dominant methanogenic pathway producing diagenetic carbonates with delta sup 13 c values up to 27 pdb this example shows the inherent problems of interpreting bulk samples with progressive mineralogical sequences of calcite to mg calcite to aragonite to dolomite merely in terms of mg sup 2 ca sup 2 in lake waters it provides a model for the interpretation of ancient lacustrine carbonates from organic rich environments

subaqueous sediment gravity flow deposits practical criteria for their field description and classification a new method for the description and classification of subaqueous sediment gravity flow deposits is proposed the classification scheme employs a convenient letter code and divides deposits individual beds into descriptive categories of two hierarchical levels facies and subfacies facies as the higher rank categories are distinguished chiefly on the basis of sediment type i e bed grain size texture a total of 13 facies have been distinguished g gravel gs gravel sand couplet gys gravelly sand s sand sm sand mud couplet ms mud sand couplet tm silt mud couplet mt mud silt couplet m mud mys muddy sand sym sandy mud myg muddy gravel gym gravelly mud subfacies as the lower rank categories are distinguished within the individual facies on the basis of the bed s internal structures the number of subfacies is unlimited and their labelling code includes particular facies symbols see above preceded by lower case letters denoting specific sedimentary structures and their vertical arrangement subfacies thus refer to the bed s intervals or divisions which are labelled as follows m massive unstratified and ungraded g graded unstratified and graded s plane stratified x cross stratified 1 parallel and or cross laminated q liquefied for example subfacies gsg graded to plane stratified gravel are gravel beds that have a lower graded interval and an upper plane stratified interval subfacies xg cross stratified gravel are gravel beds that are cross stratified throughout subfacies sls plane stratified to laminated sand are sand beds that have a lower plane stratified interval and an upper laminated parallel and or cross laminated interval

palustrine sedimentation in an episodically subsiding basin the miocene of the northern teruel graben spain lacustrine deposits form most of the sedimentary record accumulated throughout the miocene in the northern part of the teruel graben a landlocked basin situated in ne spain three main stratigraphic units units i iii spanning late vallesian to late turolian in age are distinguished in the area the two former units comprise mainly carbonate lacustrine deposits that were deposited in a palustrine or a more permanent but shallow lacustrine setting the latter being related mainly to periods of lake expansion under more humid and cooler climatic conditions in contrast deposition of unit iii characterised by gypsiferous lacustrine sediments in central parts of the basin reflects the influence of source rocks of evaporitic nature upper triassic formations that were emplaced by diapiric uplift in the eastern margin during the middle turolian carbonate lake sediments belonging to units i and ii consist of four main lithofacies associations a distal alluvial lake margin deposits b lacustrine carbonates and pedogenically modified lacustrine carbonates c carbonate fill channels and d organic rich marlstone and carbonate marshes lithofacies association a shows typically a sequential arrangement formed from bottom to top of red mudstone carbonate palaeosols and biomicrite beds sequence type 1a these sequences are interpreted as a result of slow but continuous aggradation of the floodplain areas and subsequent rise of the water table probably reflecting equilibrium between subsidence and sedimentation lithofacies association b consisting of biomicrite beds passing upward into palaeosols sequence type 1b is thought to be caused by marked pulses of tectonic subsidence that created the accommodation space required for fast development of a carbonate lake carbonate fill channels showing erosive lower surfaces dig out on previous channels marsh deposits and or lacustrine carbonates exhibit well developed prismatic structure at their bed tops the sequential arrangement suggests similar tectonic constrains than the envisaged for lithofacies 1b the comparison of depositional styles of the lake systems with the palaeoclimatic evolutionary pattern of the basin throughout the miocene indicates that the combined effect of tectonism climate and source rock played a major role in the stratigraphic framework of the basin during this period

linking the spatial distribution of bed load transport to morphological change during high flow events in a shallow braided river this paper provides novel observations linking the connections between spatially distributed bed load transport pathways hydraulic patterns and morphological change in a shallow gravel bed braided river these observations shed light on the mechanics of braiding processes and illustrate the potential to quantify coupled material fluxes using remotely sensed methods the paper focuses upon a 300 m long segment of the rees river new zealand and utilizes spatially dense observations from a mobile acoustic doppler current profiler adcp to map depth velocity and channel topography through a sequence of high flow events apparent bed load velocity is estimated from the bias in adcp bottom tracking and mapped to indicate bed load transport pathways terrestrial laser scanning tls of exposed bar surfaces is fused with the adcp surveys to generate spatially continuous digital elevation models which quantify morphological change through the sequence of events results map spatially distributed bed load pathways that were likely to link zones of erosion and deposition the coherence between the channel thalweg zone of maximum hydraulic forcing and maximum apparent bed load pathways varied this suggests that in places local sediment supply sources exerted a strong control on the distribution of bed load distinct from hydraulic forcing the principal braiding mechanisms observed were channel choking leading to subsequent bifurcation results show the connection between sediment sources pathways and sinks and their influence on channel morphology and flow path directions the methodology of coupling spatially dense adcp surveys with tls has considerable potential to understand connections between processes and morphological change in dynamic fluvial settings

late quaternary lacustrine groundwater aeolian and pedogenic gypsum in the prungle lakes southeastern australia abstract detailed petrographic studies of recent or sub recent evaporites where many critical environmental parameters are defined can help in the analysis of ancient deposits and in the establishment of chemical and environmental models for evaporite formation the prungle lakes are part of the now dry willandra lakes system in semi arid southwestern new south wales the willandra lakes have been a site of cyclic quaternary sedimentation in response to the well documented global climatic fluctuations associated with the glacial interglacial cycle at times of hydrologic stress low lake levels are associated with high salt volumes inherited from evaporative concentration in large shallow lakes upstream and the inflow of saline groundwaters thus at prungle a complex array of concentric shorelines lake floor terraces and lunettes has developed as basin within basin landforms which formed in response to filling and drying cycles sediments associated with these geomorphic units include 1 1 freshwater littoral nearshore and deep water deposited laminated sands and muds with biogenic carbonates chiefly of ostracodal and algal origin 2 2 evaporites comprising interbedded clay and laminated gypsum clay couplets which consist of discrete thin laminae of sugary white euhedral prismatic gypsum separated by detrital clay layers with a high degree of optical orientation primary accessory celestite srso4 occurs as discrete patches within the gypsum laminae 3 3 groundwater pyramidal discoidal or lenticular gypsum crystals grown from supersaturation produced by evaporation at the capillary fringe of the water table these have formed displacively within the sediments and caused considerable disruption of the sediment matrix 4 4 aeolian deposition in irregular transverse ridges of sand sized reworked groundwater gypsum and disrupted lacustrine clays the gypsum crystals are predominantly discoidal pyramidal forms which are conspicuously oriented parallel to bedding well sorted and extensively corroded the clay pellets are well sorted and moderately well rounded higher in the profile bedding is indistinct due to pedogenic processes which include modification of detrital grains and secondary crystallization of gypsum and carbonate a thin gypcrete horizon occurs at the surface the last cycle of sedimentation in the prungle lakes is believed from correlation with lakes higher in the willandra system to have occurred during the period 50 000 16 000 yr b p since then groundwaters have dropped below the zone of interaction with the lake floor and surface water no longer reaches the lakes sedimentation has ceased and soil formation with secondary carbonate and gypsum has continued to the present a range of sedimentary environments is identified which depend on strong seasonal oscillations these environments are virtually absent from the australian continent today and their occurrence during the pleistocene supports the contention of enhanced climatic seasonality at that time the array of sediment types and mineralogies is almost identical to that characteristic of coastal sabkha sequences highlighting the difficulty of relying on unusual evaporative mineralogy to differentiate marine and non marine environments detailed petrographic analyses of the prungle sequence have been made in association with a review of theoretical experimental and observational studies of the environmental controls of calcium sulfate mineralogy and crystal habit this has enabled the correlation at prungle of depositional environment with gypsum petrofacies and associated compositional fabric or structural features these observations are more generally applicable to other evaporite deposits many gypsum evaporites reported in the literature have been compared with this scheme developed at prungle

paleomagnetic and inner diapiric structural constraints on the kinematic evolution of a salt wall the bicorb quesa and northern navarres salt wall segments case prebetic zone se iberia abstract paleomagnetism together with an analysis of the internal structure of the bicorb quesa and northern navarres salt wall segments prebetic zone in se iberia were used to constrain their kinematics and driving mechanisms paleomagnetic data from upper triassic red beds of the selected salt related structures and from the miocene rocks belonging to adjacent syn diapiric half grabens reveal 15 30 counter clockwise vertical axis rotations of the salt wall rocks and a 20 clockwise rotation of the jurassic miocene cover block located south of the salt wall this together with the salt wall structure indicates that the origin of the salt wall was linked to the motion of a late miocene thin skinned extensional fault system which detached on the upper triassic evaporites specifically the salt wall formed by the south southwest displacement with a 20 clockwise rotation component of a cover block bounded northwards by the detachment disruptions generated by the motion of pre existent basement faults the upper triassic detachment level was first affected by a counter clockwise vertical axis rotation and during the paleogene earliest miocene building of the iberian chain by tight wnw trending folds and sse directed minor thrusts this study also shows that paleomagnetism together with the analysis of the internal structure can successfully depict the geometry and kinematic evolution of complex salt wall structures

comparison of methods for quantifying active layer dynamics and bedload discharge in armoured gravel bed rivers several methods were employed in the ardennian rivers belgium to determine the depth of the active layer mobilized during floods and to evaluate the bedload discharge associated with these events the use of scour chains has shown that the depth of the active layer is systematically less than the b axis of the average particle size d50 of the elements which compose the surface layer of the riffles this indicates that only a partial transport exists during low magnitude floods the bedload discharge has been evaluated by combining data obtained using the scour chains technique and the distance covered by tracers quantities of sediment transported during frequent floods are relatively low 0 02 t km 2 due to the armour layer which protects the subsurface material these low values are also related to the fact that the distance calculated for mobilized bedload only applies to tracers fitted with pit passive integrated transponder tags diameter 20 mm whereas part of the bedload discharge is composed of sand and fine gravel transported over greater distances than the pebbles the break up of the armour layer was observed only once for a decennial discharge during this event the bedload discharge increased considerably 2 t km 2 the use of sediment traps data from dredging and a helley smith sampler confirm the low bedload transport in ardennian rivers in comparison to the bedload transport in other geomorphological contexts this difference is explained by the presence of an armoured layer but also by the imbricated structures of flat bed elements which increase the resistance to the flow finally the use of the old iron industry wastes allowed to quantify the thickness of the bed reworked over the past centuries in the lembree river the river bed contains slag elements up to a depth of about 50 cm indicating that exceptional floods may rework the bed to a considerable depth copyright 2012 john wiley sons ltd

scaling geology and seismic deconvolution the reflection seismic signal observed at the surface is the convolution of a wavelet with a reflection sequence representing the geology deconvolution of the observations without prior knowledge of the wavelet can be done by making assumptions about the statistics of the reflection sequence in particular the widely used prediction error filter is obtained by assuming that the power spectra of reflection sequences are white however evidence from well logs suggests that the power spectra are in fact proportional to a power of the frequency f that is to f with equal approximately to 1