the record of the messinian salinity crisis in the tertiary piedmont basin nw italy the alba section revisited abstract the alba succession tertiary piedmont basin nw italy preserves the northernmost record of the messinian salinity crisis msc and was deposited on the southern margin of a wide wedge top basin related to the involvement of the piedmont basin in the apennine compressional tectonics pre msc sediments consist of a cyclic succession of marine euxinic shales and calcareous marls deposited under the influence of precession modulated climate changes and document the progressive restriction of the basin prior to the onset of the msc they are followed by the primary lower gypsum unit plg deposited during the first msc stage from 5 96 to 5 60 ma these sediments show a clear precession related cyclic stacking pattern and record the lateral transition from a shallow water marginal setting in the sw to a deeper one in the ne in marginal settings six plg cycles are recognised truncated by an erosional unconformity placed at the base of the post evaporitic sediments the lowermost five cycles are composed of massive and banded selenite beds separated by thin shale intervals a sharp change evidenced by the appearance of the branching selenite facies is recorded by the 6th gypsum bed that represents a distinctive marker bed here called sturani key bed that can be mapped throughout the study area basinward the lower plg cycles are transitional to decimetre thick carbonate rich layers interbedded to euxinic shales that are overlain by the sturani key bed above the marker bed other seven plg cycles are present the gypsum beds form thinner bodies compared to the sturani key bed and are characterised by a greater amount of fine grained terrigenous fraction suggesting an increase of continental runoff related in turn to humid climate conditions at the end of the first msc stage plg cycles are followed by slumped mudstones and clastic gypsum beds that correspond to the resedimented and chaotic facies resedimented lower gypsum deposited in the mediterranean basins during the second msc stage from 5 60 to 5 55 ma they are in turn overlain by continental and brackish water facies with lago mare fossil assemblages recording the final stage of the msc the messinian succession of alba provides the opportunity to reconstruct the lateral facies transition between marginal and distal settings and to shed new light on the deep water msc sedimentary record moreover the appearance of the branching selenite facies from the 6th plg cycle upward provides a tool for properly placing the piedmont record in the msc chronostratigraphic framework allowing us to investigate the influence of climate gradients on the sedimentary response to the mediterranean salinity crisis

reconstruction of eroded and deposited sediment volumes of the embanked river waal the netherlands for the period ad 1631 present in the last few centuries humans have modified rivers and rivers have responded with noticeable changes in sedimentary dynamics the objective of this study is to assess these responses of the sedimentary dynamics therefore we calculated a sediment budget for eroded and deposited sediment volumes in a similar to 12 km long floodplain section of the largest semi natural embanked but still dynamic lower rhine distributary for similar to 50 years time slices between ad 1631 and present this is the period during which embanked floodplains were formed by downstream migration of meander bends between confining dykes our sediment budget involves a detailed reconstruction of vertical and lateral accretion rates and erosion rates of floodplain sediment to do so we developed a series of historical geomorphological maps and lithogenetic cross sections based on the maps and cross sections we divided the floodplain into building blocks representing channel bed and overbank sediment bodies chronostratigraphy within the blocks was estimated by interpretation of heavy metal profiles and from optically stimulated luminescence osl dating results sediment budgets were hence calculated as a change of volume of each building block between time steps the amount of lateral accretion initially increased as a result of island and sand bar formation following embankment from the eighteenth century onwards there was a decrease of lateral processes in time which is a result of straightening of the river by human activities and a reduction of water and sediment supply due to the construction of a new upstream bifurcation with straightening of the river the floodplain area grew artificial fixation of the channel banks after ad 1872 prevented lateral activity from then on overbank deposition became the main process leading to a continuous increase of floodplain elevation and inherent decrease of flooding frequency and sediment accumulation rate copyright c 2014 john wiley sons ltd

the gibraltar corridor watergate of the messinian salinity crisis abstract the existence and evolution of a messinian salt giant in the mediterranean sea has caused much debate in the marine science community especially the suggestion that the mediterranean was a deep desiccated basin during the messinian salinity crisis msc 5 97 5 33 ma triggered by a temporal disconnection from the global ocean made it a well known crisis beyond the scientific boundaries approximately 50 years after this provocative statement it remained unknown which mediterranean atlantic seaway delivered the 5 6 of the global ocean s salt into the mediterranean basin here we review the changes in mediterranean atlantic connectivity throughout the late miocene in order to locate date and quantify the missing messinian gateway that provided the salt water inflow during the msc we conclude that all the known pre msc gateways through southern spain and northern morocco were closed leaving the gibraltar corridor at its messinian configuration as the sole candidate we consider the possibility of longer and narrower straits existing at depth below the present gibraltar region and using strait dynamic theory we calculate its dimensions during the messinian based on the salinity changes in the mediterranean a marine messinian gateway through the gibraltar corridor is in agreement with growing evidence that atlantic waters reached the mediterranean sea during all three stages of the msc

the tidally averaged momentum balance in a partially and periodically stratified estuary abstract observations of turbulent stresses and mean velocities over an entire spring neap cycle are used to evaluate the dynamics of tidally averaged flows in a partially stratified estuarine channel in a depth averaged sense the net flow in this channel is up estuary due to interaction of tidal forcing with the geometry of the larger basin the depth variable tidally averaged flow has the form of an estuarine exchange flow downstream at the surface upstream at depth and varies in response to the neap spring transition the weakening of the tidally averaged exchange during the spring tides appears to be a result of decreased stratification on the tidal time scale rather than changes in bed stress the dynamics of the estuarine exchange flow are defined by a balance between the vertical divergence of the tidally averaged turbulent stress and the tidally averaged pressure gradient in the lower water column in the upper water column tidal stresses are important contributors particularly during the n

late highstand patterns of shifting and stepping coastal barriers and washover fans late messinian sorbas basin se spain abstract the late messinian sorbas member up to 75 m thick consists in its type area of a parasequence set of three prograding coastal barriers sequences i iii associated with lagoon and washover sediments around the town of sorbas these strata can be studied exceptionally well due to absence of burrowing by raised messinian salinities and exposure along a network of up to 30 m deep canyons fifteen vertical sections were logged and carefully correlated this permits to reconstruct and discuss patterns of relative sea level movements between decimetres up to 15 m within a parasequence excellent examples of non tidal transgressive facies are characterized by lagoon and washover sediments instead of the usual combination of washover and tidal deposits channel and flood tidal delta implications for the sandstone connectivity are given the lower two sequences are deposited in a relatively large tectonically enhanced wedge shaped accommodation space they show both fining up deepening sequences followed by prograding coarsening up shoaling sequences and can be compared to the classical parasequences of the western interior basin usa progradation of sequence ii was interrupted by a major slide event most likely triggered by an earthquake which caused more than 400 m seaward slumping of a stretch of 1 km of coastal sands the architecture of sequence iii is more complex due to limited accommodation space characteristic for the late highstand so that this setting was very sensitive to sea level fluctuations this resulted in an intricate pattern of juxtaposed and superposed lagoonal muds washover fans and swash zones so called stranded coastal barriers occur which were left behind after seaward jump of the coastline over more than 1 5 km during forced regression the pattern of reconstructed sea level positions is well comparable to the sequential pattern shown by the correlated equivalents along the northern basin margin which belong to the so called terminal carbonate complex the problem of ranking the complex sequence iii as one or more parasequences and its consequences for cyclostratigraphy are shortly discussed two models of washover formation are given respectively during more rapid and more slow sea level rise the influence of synsedimentary folding on the location of barriers is discussed and also the source area of extra and intraclasts supplied to barriers and washovers after deposition of the sorbas member the sea withdrew from the sorbas basin probably as a result of the major downdrop in the mediterranean at the maximum isolation during the salinity crisis it is suggested that the semi enclosed setting of the basin resulted only in limited localized erosion in contrast to the deeper adjacent vera basin which was more open to the mediterranean

geomorphology within the interdisciplinary science of environmental flows article i nfo the field tradition in geomorphology informs beyond studying landforms by also providing a stage for understand ing how geomorphic elements influence the ecology of biota the intersection between fluvial geomorphology and riverine ecology represents an ideal confluence to examine the contribution of the geomorphic field tradition to en vironmental flows and show this area of riverine management as a research frontier for applied geomorphology environmental flows have consisted of a set of ecological based stream flow guidelines designed to inform sustain able water resource management that supports healthy riverine habitats and provides sufficient water supply for society geomorphological understanding is central to environmental flows because it is the interaction between flow form and substrate that influences habitat type condition availability and biotic use across space and time this relationship varies longitudinally laterally vertically overtime and across macro to mesoscale morphologies withintheriverine environment thegeomorphictemplateis therefore asintegralasthe flow wereviewedstudies where field evidence indicated that geomorphology impacts the effectiveness of environmental flow strategies and wemakethecasefortheneedtoincreasegeomorphic considerationsinenvironmental flows although flow iscom monly referred toas themaster variablein environmental flows geomorphologymediatestheeffectsof flow regime on ecological processes concepts and applications from this perspective on the role of geomorphology in riverine ecosystem research will inform the practice policy and implementation of environmental flows

processes of arroyo filling in northern new mexico usa we documented arroyo evolution at the tree trench and arroyo scales along the lower rio puerco and chaco wash in northern new mexico usa we excavated 29 buried living woody plants and used burial signatures in their annual rings to date stratigraphy in four trenches across the arroyos then we reconstructed the history of arroyo evolution by combining trench data with arroyo scale information from aerial imagery light detection and ranging lidar longitudinal profiles and repeat surveys of cross sections burial signatures in annual rings of salt cedar and willow dated sedimentary beds greater than 30 cm thick with annual precision along both arroyos incision occurred until the 1930s in association with extreme high flows and subsequent filling involved vegetation development channel narrowing increased sinuosity and finally vertical aggradation a strongly depositional sediment transport regime interacted with floodplain shrubs to produce a characteristic narrow trapezoidal channel the 55 km study reach along the rio puerco demonstrated upstream progression of arroyo widening and filling but not of arroyo incision channel narrowing or floodplain vegetation development we conclude that the occurrence of upstream progression within large basins like the rio puerco makes precise synchrony across basins impossible arroyo wall retreat is now mostly limited to locations where meanders impinge on the arroyo wall forming hairpin bends for which entry to and exit from the wall are stationary average annual sediment storage within the rio puerco study reach between 1955 and 2005 was 4 8 10 5 t yr 16 of the average annual suspended sediment yield and 24 of the long term bedrock denudation rate at this rate the arroyo would fill in 310 yr

storage filters upland suspended sediment signals delivered from watersheds climate change tectonics and humans create long and short term temporal variations in the supply of suspended sediment to rivers these signals generated in upland erosional areas are filtered by alluvial storage before reaching the basin outlet we quantified this filter using a random walk model driven by sediment budget data a power law distributed probability density function pdf to determine how long sediment remains stored and a constant downstream drift velocity during transport of 157 km yr for 25 km of transport few particles are stored and the median travel time is 0 2 yr for 1000 km of transport nearly all particles are stored and the median travel time is 2 5 m y both travel time distributions are power laws the 1000 km travel time distribution was then used to filter sinusoidal input signals with periods of 10 yr and 10 4 yr the 10 yr signal is delayed by 12 5 times its input period damped by a factor of 380 and is output as a power law the 10 4 yr signal is delayed by 0 15 times its input period damped by a factor of 3 and the output signal retains its sinusoidal input form but with a power law tail delivery time scales for these two signals are controlled by storage in channel transport time is insignificant and low frequency signals are transmitted with greater fidelity than high frequency signals these signal modifications are essential to consider when evaluating watershed restoration schemes designed to control sediment loading and where source area geomorphic processes are inferred from the geologic record

the abad composite se spain a messinian reference section for the mediterranean and the apts a high resolution integrated stratigraphy is presented for the abad marls of the sorbas and nijar basins in se spain preevaporitic messinian of the western mediterranean detailed cyclostratigraphic and biostratigraphic analyses of partially overlapping subsections were needed to overcome stratigraphic problems in particular encountered at the complex transition from the lower to the upper abad the resulting abad composite section contains a continuous stratigraphic record from the tortonian messinian boundary up to the transition to the messinian evaporites of the yesares member all together 18 calcareous plankton events were recognized which were shown to be synchronous throughout the mediterranean by means of detailed bed to bed cyclostratigraphic correlations the magnetostratigraphy allowed the identification of the four magnetic reversals of chron c3an in the upper abad details in the sedimentary cycle patterns allowed the abad composite to be astronomically calibrated this calibration to the 658n summer insolation curve of solution la90 1 1 yielded astronomical ages for all sedimentary cycles calcareous plankton bioevents ash layers and paleomagnetic reversals up to now the abad composite is the only astronomically well calibrated section that provided a reliable cyclostratigraphy magnetostratigraphy and calcareous plankton biostratigraphy as such it will serve as a reference section both for the pre evaporite messinian in the mediterranean as well as for the messinian interval in the astronomical polarity time scale q 2001 elsevier science b v all rights reserved

extending the astronomical polarity time scale into the miocene an astronomical time scale is presented for the late miocene based on the correlation of characteristic sedimentary cycle patterns in marine sections in the mediterranean to the 65 n summer insolation curve of la90 1 2 with present day values for the dynamical ellipticity of the earth and tidd dissipation by the moon this correlation yields ages for all sedimentary cycles and hence also for the recorded polarity reversals and planktonic foraminiferal and dinoflagellate events the tortonian messinian t m boundary placed at the first regular occurrence of the globorofuliu conomiozea group in the mediterranean is dated at 7 24 ma the duration of the messinian is estimated at 1 91 myr because the miocene pliocene boundary has been dated previously at 5 33 ma 3 the new time scale is confirmed by oar 3gar ages of volcanic beds and by the number of sedimentary cycles in the younger part of the mediterranean messinian

3d modelling of the sorbas basin spain new constraints on the messinian erosional surface morphology abstract the scenario of the messinian salinity crisis msc remains one of the most debated topics in the mediterranean realm and especially in the sorbas basin which is one of the type localities of msc related deposits after a recently improved chronostratigraphic framework of the miocene and pliocene deposits of the basin this work is an attempt to image the morphology of the messinian erosional surface mes at depth we built a basin scale 3d model of the miocene and pliocene series that confirms the erosional character of the messinian pliocene boundary solving a long standing and debated question we tentatively also suggest that the fluvial system developed during the peak of the msc was exiting the basin toward the south this new geometrical model showing a robust internal consistency can be used as a basis for interpreting the messinian salinity crisis in other sedimentary basins around the mediterranean sea the return of marine conditions in the early pliocene on an erosional surface interferes with the continuous formation of the sorbas basin asymmetrical syncline subsidence of the hinge uplift of the limbs and gravitational sliding the irregular shape of the mes is superimposed in the southern part of the basin by small scale box type folds with two oblique nne ssw and wnw ese fold axes directions the architecture of these folds suggests gravitational sliding of post evaporitic marine sediments during the progressive deformation of the basin during the zanclean

mediterranean messinian salinity crisis constraints from a coeval marginal basin sorbas southeastern spain abstract the extent timing and effects of late miocene desiccation and evaporite deposition in the mediterranean sea remain controversial marginal basins containing messinian 5 3 7 1 ma sequences now exposed onland supplement information from the deep mediterranean but have evaporites of a variety of ages some of these messinian evaporites pre date and others post date deep desiccation none appears to be exactly coeval with those of the deep mediterranean in the betic cordillera of southern spain basins e g granada basin far from the present day mediterranean lost connection with the mediterranean due to uplift 1 ma before the salinity crisis and have marine evaporites of early not late messinian age in contrast basins such as the sorbas basin in southeastern spain adjacent to the present day mediterranean record events directly reflecting the course of the salinity crisis the sorbas basin retained marine connection with the western mediterranean up until evaporative drawdown in the mid messinian and was rapidly reflooded immediately afterwards the sorbas messinian sequence is up to 320 m thick it is complete and normal marine except for an incised basinwide erosion surface overlain by a 130 m thick gypsum deposit we propose that this surface marks the interval of deep desiccation of the adjacent mediterranean basin erosion occurred shortly after 5 9 ma and the irregular unconformity has relief of at least 240 m confirming mediterranean drawdown significantly below the atlantic level sorbas gypsum deposits overlie the unconformity and are intercalated with marls estimated at 5 5 ma containing normal marine messinian biotas these gypsum deposits therefore post date deep desiccation and formed in a silled basin immediately following marine reflooding they mark the end of the salinity crisis and are overlain by 70 m of normal marine sediments containing unreworked foraminifers of latest messinian age this succession demonstrates that the salinity crisis occurred faster and was completed sooner than previously believed it took place within 0 4 ma time scale of berggren et al 1995b is 0 2 ma on the time scale of baksi 1993 and was completed before the end of the messinian this corrects previous views that the salinity crisis continued until the early pliocene there is no evidence in the sorbas basin for brackish lago mare conditions and the normal marine biotas that directly precede and follow drawdown rebut earlier suggestions of prolonged salinity effects

the upper tortonian lower messinian at monte dei corvi northern apennines italy completing a mediterranean reference section for the tortonian stage abstract a high resolution integrated stratigraphy including biostratigraphy magnetostratigraphy tephrostratigraphy and cyclostratigraphy is presented for the upper tortonian and lower messinian upper miocene at monte dei corvi numerical age control comes from a combination of magnetobiostratigrapic dating and astronomical tuning while radioisotope dating of ash layers produced less reliable ages the deep marine succession is characterized by large scale non repetitive stratigraphic changes allowing the discrimination between a lower brownish rossini and euxinic shale interval the sedimentary cycles which occur superimposed on these large scale changes are related to astronomical climate forcing astronomical tuning of the sedimentary cycles provides not only absolute ages for biostratigraphic events reversal boundaries and volcanic ash layers but also for the observed non cyclic changes these can be linked to environmental and geodynamic changes in the mediterranean region preceding the messinian salinity crisis the beginning of the brownish interval marked by tripartite cycles at 8 017 ma coincides with tectonic re arrangements in the mediterranean such as compression in the betics and opening of the rifian corridor at 7 616 ma the change to the calcareous rossini interval can be linked to tectonic uplift in the northern apennines and the deepening of the rifian corridor while the betic corridor became restricted coinciding with the end of evaporite deposition in the eastern betics the change to euxinic shales at 7 168 ma reflects basin wide restriction marked by diatomite and sapropel formation in the mediterranean basin related to the severely constricted betic and rifian corridors the occurrence of a tripartite construction of cycles in the euxinic shales at 6 719 ma coincides with diatomite formation in the eastern mediterranean uplift and shallowing in the northern apennines and further constriction of the atlantic gateways we conclude that late tortonian early messinian tectonic and environmental events occur remarkably synchronously in the mediterranean basin and most likely result from a combination of geodynamic processes and eccentricity controlled climatic changes in combination with the upper serravallian and lower tortonian interval which includes the formal tortonian global stratotype section and point gssp the monte dei corvi is the only complete section in the mediterranean covering the entire tortonian stage we therefore propose the monte dei corvi section as tortonian reference section particularly for the mediterranean region in addition it may serve as a unit stratotype for the tortonian

messinian carbonate rich beds of the tertiary piedmont basin nw italy microbially mediated products straddling the onset of the salinity crisis abstract the seven messinian microbial carbonate rich layers cropping out in the pollenzo section tertiary piedmont basin nw italy are interbedded with a precession related cyclic succession composed of euxinic shale marl couplets and straddle the onset of the messinian salinity crisis msc a sharp change of sedimentological compositional and geochemical characteristics was observed from the onset of the msc onward suggesting strong differences in the mechanisms responsible for carbonate precipitation pre msc beds are mainly composed of dolomite and are interpreted as the product of early diagenesis formed by bacterial sulphate reduction in the shallow subsurface along the sulphate methane interface dolomite precipitation was temporarily enhanced by an upward flux of methane rich fluids possibly sourced by gas hydrate destabilisation conversely from the onset of the msc onward carbonate beds are thinly laminated and show abundant filaments interpreted as beggiatoa like bacteria while calcite and aragonite are the dominant authigenic phases these beds are interpreted as microbialites resulting from the lithification of chemotrophic bacterial mats dominated by sulphide oxidizing bacteria the carbonate necessary for their preservation was provided by bacterial sulphate reduction these microbialites that appear as the deeper water counterpart of bottom grown selenite layers deposited in the marginal part of the basin formed on an anoxic sea bottom under a density stratified water column the high sulphate concentration in the pore waters related to the presence of concentrated brines and to the regeneration of sulphate by sulphide oxidizing bacteria is considered as the driving factor controlling the mineralogical change from dolomite to calcite and aragonite finally the sharp shift towards negative 18 o values of carbonates observed from the onset of the msc onward was probably related to fractionation processes operated by sulphate reducing bacterial communities in the pore waters this suggests that care must be taken when dealing with microbial carbonates in the interpretation of the oxygen isotope values in terms of fluctuating salinity condition of the water mass in conclusion this study suggests that the onset of the msc had a strong impact on microbial populations governing carbonate precipitation in a sector of the basin dominated by depositional conditions not suitable for gypsum precipitation

late miocene mediterranean desiccation topography and significance of the salinity crisis erosion surface on land in southeast spain comment one of the most striking aspects of the mediterranean messinian salinity crisis as observed in landbased sections is the basin wide synchronicity in facies change krijgsman et al 1999a the messinian succession of the caltanisetta basin on sicily serves as the classical standard for these facies changes which can also be recognised elsewhere in the mediterranean i e on cyprus crete northern italy and southern spain it starts with an alternation of open marine marls and sapropels passes via diatomites into evaporitic limestones gypsum and halite of the lower evaporites of marine origin and following an erosional unconformity ends with the upper evaporites and associated fresh to brackish water deposits of the lago mare that are essentially of non marine origin and contain a caspi brackish ostracode fauna the erosional unconformity between the lower and upper evaporites is assumed to reflect the phase of most extreme sea level drawdown in the mediterranean that caused significant erosion and localised channel entrenchment on the continental shelves and slopes

record of the messinian salinity crisis in the sw mallorca area balearic promontory spain the current interpretation of the messinian salinity crisis msc involves the deposition of the so called peripheral or marginal evaporites in onshore basins as well as the erosion of the margins and the formation of thick evaporites in the deep parts of the basins the present study focuses on intermediate depth basins i e located between the onshore outcrops and the deep basins indeed the balearic promontory shows small stepped basins filled with msc deposits between its western extremity on the alicante shelf and its eastern end around the menorca block new and already available seismic reflection profiles and onshore data allow us to investigate the nature and geometrical relationships of these deposits in the area between the islands of ibiza and mallorca our observations suggest the existence of three msc related units in this area the lowermost transparent seismic unit can be interpreted as a 100 to 200 m thick salt layer deposited in the deepest part of the central mallorca depression these evaporites pass laterally and upward into a thin bedded seismic unit which could be lithologically equivalent to the upper evaporites of the deep basins all around the borders of the central mallorca depression this bedded seismic unit onlaps a slope unit which shows bedded to chaotic and rafted facies the messinian continental shelf is eroded and incised by a valley extending from the palma onshore area to the mallorca downslope domain our results suggest the presence offshore of at least two generations of diachronous msc deposits the observation of salt on a continental high and the widespread msc deposits on the margins of the central mallorca depression call into question the location of halite preferentially in the deep abyssal basins and the significance of the deep basin msc units that onlap onto the margin erosional surface mes as observed all around the passive margins of the northwest mediterranean basin the dual terminology used for peripheral deep msc evaporites cannot be applied to any of the msc units found in the study area

isotope stratigraphy 87sr 86sr δ18o δ13c of the sorbas basin betic cordillera spain paleoceanographic evolution across the onset of the messinian salinity crisis abstract the sorbas basin is a reference sector of the mediterranean basin for the definition of the onset of the messinian salinity crisis straddling the transition from the open marine deposits abad marls to the primary lower gypsum yesares formation during the first stage of the crisis between 5 97 and 5 60 ma because of its proximity to the atlantic gateway the sorbas basin is pivotal for the study of the oceanographic evolution that led to the most dramatic environmental event in the mediterranean sea we measured the carbon 13 c oxygen 18 o and strontium 87 sr 86 sr isotope ratio of 50 samples of planktonic foraminifera mollusk shells gypsum and carbonate sediments from the abad and yesares members turre and canos formation in the perales hueli los yesos and rio de aguas sections our results show a long term trend with most of the values plotting within the range of the global ocean strontium isotope curve and distinct short term fluctuations on precessional time scale the investigated geochemical proxies suggest that these oscillations reflect significant input of continental waters into the basin during the humid phase of a single precessional cycle this implies that the western mediterranean did not experience a main disconnection from the global ocean water before and during the first stage of the messinian salinity crisis and that different milankovitch forcings played a significant role in determining the seawater geochemistry

a 184 year record of river meander migration from tree rings aerial imagery and cross sections abstract channel migration is the primary mechanism of floodplain turnover in meandering rivers and is essential to the persistence of riparian ecosystems channel migration is driven by river flows but short term records cannot disentangle the effects of land use flow diversion past floods and climate change we used three data sets to quantify nearly two centuries of channel migration on the powder river in montana the most precise data set came from channel cross sections measured an average of 21 times from 1975 to 2014 we then extended spatial and temporal scales of analysis using aerial photographs 1939 2013 and by aging plains cottonwoods along transects 1830 2014 migration rates calculated from overlapping periods across data sets mostly revealed cross method consistency data set integration revealed that migration rates have declined since peaking at 5 m year in the two decades after the extreme 1923 flood 3000 m 3 s averaged over the duration of each data set cross section channel migration occurred at 0 81 m year compared to 1 52 m year for the medium length air photo record and 1 62 m year for the lengthy cottonwood record powder river peak annual flows decreased by 48 201 vs 104 m 3 s after the largest flood of the post 1930 gaged record 930 m 3 s in 1978 declining peak discharges led to a 53 reduction in channel width and a 29 increase in sinuosity over the 1939 2013 air photo record changes in planform geometry and reductions in channel migration make calculations of floodplain turnover rates dependent on the period of analysis we found that the intensively studied last four decades do not represent the past two centuries

tidal and residual circulations in coupled restricted and leaky lagoons abstract finite element numerical modelling based on field data is used to study the tidal and tidally induced residual circulation dynamics of a coupled restricted and leaky coastal lagoon system located in the magdalen islands gulf of saint lawrence havre aux maisons lagoon hml is of a restricted nature with a neutral inlet in terms of tidal asymmetry grande entree lagoon gel is of a leaky nature with a marked ebb dominance at the inlet due to direct interactions between the main astronomical tidal constituents the imbalance caused by the different tidal filtering characteristics of both inlets combines with the internal morphological asymmetries of the system to produce a residual throughflow from hml to gel the residual circulation is also characterized by strongest values at both inlets very weak residual currents in hml deep basin and a dipole of residual eddies over the deeper areas of gel further investigations including numerical tracer experiments will be necessary to achieve a full understanding of the long term circulation of this lagoonal system

the deep water counterpart of the messinian lower evaporites in the apennine foredeep the fanantello section northern apennines italy abstract a possible deep water non evaporitic unit equivalent of the messinian lower evaporites has been recognised in the northern apennine foredeep this unit whose existence is implicitly admitted in the two step model of the mediterranean messinian salinity crisis is documented here for the first time it occurs throughout the apennine foredeep basin below a thick horizon of resedimented gypsum deposits usually ascribed to the lower evaporites actually the lower evaporites of the apennine foredeep basin include both shallow water in situ precipitated facies and deep water resedimented facies deposited in distinct depocenters the usually envisaged coeval nature of the two deposits has been recently challenged in several works based on a physical stratigraphic considerations about the downbasin correlation of the messinian erosional surface cutting on top the in situ evaporites with the sharp base of the resedimented evaporites unit and b the common occurrence of a barren unit below the resedimented evaporites which has no obvious equivalents in pre evaporitic successions underlying the in situ precipitated evaporites in this work a multidisciplinary study has been carried out on a 140 m thick composite section fanantello section to definitely assess the age and palaeoenvironmental characteristics of the unit underlying the resedimented gypsum deposits the topmost part of the section comprises a 60 m thick succession of barren euxinic shales falling entirely within a reversed polarity chron and characterised by a the complete disappearance of foraminifera b the occurrence of high salinity tolerant thecosomatous pteropods creseis sp c the abundance peaks of the calcareous nannofossil sphenolithus abies interpreted as related to highly stressed likely hyperhaline conditions d the appearance of hyperhaline and or stratified water molecular indicators gammacerane based on a multidisciplinary integrated stratigraphic approach this barren interval is here proposed to be a deeper water time equivalent of the in situ primary lower evaporites thus allowing to assess the events connected to the onset and the first phase of the messinian salinity crisis from a basinal perspective these data lend support to the hypothesis that the resedimented evaporite deposits of the apennine foredeep basin postdate the in situ evaporites thus implying that the term lower evaporites actually comprises rock bodies with different origins and separated in time and space by the messinian erosional surface and its correlative conformity this could be true also for other mediterranean basins where the stratigraphy of deep water successions should be carefully re examined

correlations and sequence stratigraphic model for messinian carbonate platforms of the western and central mediterranean distance correlations of late tortonian messinian littoral carbonate complexes are proposed from the study of eight platforms in the western and central mediterranean correlations are based on the identification of two major biological sedimentary cycles and of two index surfaces surface a is a maximum flooding surface during cycle 1 at around 6 7 ma surface b is a regional marine planation surface at around 5 95 ma at the base of cycle 2 terminal carbonate complex a general sedimentary model is proposed for the 7 5 6 ma time span the boundary between cycles 1 and 2 is coincident with the onset of the messinian salinity crisis and appears to be related to major environmental paleo oceanographic changes in the mediterranean rather than to a major sea level drop or to climatic change

the messinian salinity crisis in the adriatic foredeep evolution of the largest evaporitic marginal basin in the mediterranean abstract the recent release of a large number of subsurface geological data by the italian minister of economic development including boreholes and seismic profiles provided the occasion for a new assessment of the deposits associated with the messinian salinity crisis msc in the adriatic foreland basin system and a new integration with the outcropping successions of the apennines in particular the study of the messinian evaporites allowed to reconstruct a new detailed palaeogeographic and palaeobathymetric framework for all the stages of the crisis we identified the largest evaporitic marginal basin ever described for the mediterranean hosting the precipitation of the primary shallow water gypsum deposits plg primary lower gypsum during the first stage of the crisis during the second and third stages of the crisis the plg basin underwent uplift and erosion and the evaporite accumulation moved to the deeper part of the basin and was characterized by the deposition of the resedimented lower gypsum unit including clastic evaporites recycling the plg ones primary halite and terrigenous deposits the distribution of the different evaporitic facies was the basis for an improved reconstruction of the upper miocene tectonic evolution of the apennines thrust belt our results show a clear separation between shallower depocenters located in the wedge top and in the adriatic foreland basins and characterized by msc stage 1 plg deposition and deeper water ones located in the adriatic foredeep and close to the calabrian arc where msc stage 2 terrigenous and gypsum bearing clastic deposits and primary halite accumulated

astrochronology for the messinian sorbas basin se spain and orbital precessional forcing for evaporite cyclicity the sorbas basin of se spain contains one of the most complete sedimentary successions of the mediterranean reflecting the increasing salinity during the messinian salinity crisis a detailed cyclostratigraphic study of these successions allows a correlation of the sedimentary cycle patterns to astronomical target curves here we present an astrochronological framework for the messinian of the central part of the sorbas basin this framework will form a solid basis for high resolution correlations to the marginal carbonate facies and to the central mediterranean area the early messinian abad member contains 55 precession induced sedimentary cycles marked by homogeneous marl opalrich bed alternations in the lower abad and by homogeneous marl sapropel alternations in the upper abad astronomical tuning results in an age of 5 96 ma for the transition to the yesares evaporites and thus for the onset of the messinian salinity crisis the marl sapropel cycles of the upper abad are replaced by gypsum sapropel cycles 14 in the yesares member indicating that the evaporite cyclicity is related to precession controlled oscillations in circum mediterranean climate as well as a consequence gypsum beds correspond to precession maxima insolation minima and relatively dry climate sapropelitic marls to precession minima insolation maxima and relatively wet climate an alternative glacio eustatic obliquity control for evaporite cyclicity can be excluded because the number of sedimentary cycles with a reversed polarity is too high sedimentation during the abad yesares and the overlying coastal sequences of the sorbas member took place in a continuously marine environment indicating that marine conditions in the sorbas basin prevailed at least until 5 60 5 54 ma according to our scenario deposition of the yesares and sorbas member took place synchronously with deposition of the lower evaporites in the central mediterranean finally the continental zorreras member consists of 8 sedimentary cycles of alternating reddish silts dry climate and yellowish sands wet climate which correlates very well with the upper evaporites and lago mare facies of the mediterranean q 2001 elsevier science b v all rights reserved

stratigraphic relationships between shallow water carbonates and primary gypsum insights from the messinian succession of the sorbas basin betic cordillera southern spain abstract the lack of modern analogues for the thick primary selenite gypsum deposits formed in the mediterranean area limits the understanding of the messinian miocene evaporitic systems and particularly of their lateral relationships their evolution through time and their related ecosystems some complex stratigraphic relationships of these extreme environments are revealed in the messinian canos formation along the northern flank of the sierra alhamilla at the southern boundary of the sorbas basin southern spain here the bottom grown selenite gypsum beds pinch out against graded clastic carbonate beds ooid grainstones rudstones and mudstones emplaced by gravity flows we infer that these tabular bodies formed along a low gradient ramp derived from the periodic erosion of coeval shallow water to coastal carbonate factories located on top of the sierra alhamilla ridge the carbonate deposits bear many similarities with the terminal carbonate complex described in the northern steeper margin of the basin both deposits show a cyclical pattern given by the repetition of couplets consisting of coarser and finer grained deposits this rhythmic facies organization recalls the precessional controlled cyclic pattern of the gypsum unit clastic carbonates and gypsum were deposited during the same precessional hemicycle but appear to be mutually exclusive in fact the clastic carbonates represent the lateral equivalent of the gypsum beds or are occasionally found at their base or at both their base and top but never interstratified with them such an arrangement suggests that during the peak of the evaporitic phases a strong pycnocline acted as the top boundary for gypsum and the lower boundary for carbonate bearing gravity flows with the exception of debrites high density gravity flows and slumps these facies architectures appear to be mainly controlled by the interplay between the variable depth of the pycnocline and the density of the brine within the evaporitic cycle

refining measurements of lateral channel movement from image time series by quantifying spatial variations in registration error abstract remotely sensed data provides information on river morphology useful for examining channel change at yearly to decadal time scales although previous studies have emphasized the need to distinguish true geomorphic change from errors associated with image registration standard metrics for assessing and summarizing these errors such as the root mean square error rmse and 90th percentile of the distribution of ground control point gcp error fail to incorporate the spatial structure of this uncertainty in this study we introduce a framework for evaluating whether observations of lateral channel migration along a meandering channel are statistically significant given the spatial distribution of registration error an iterative leave one out cross validation approach was used to produce local error metrics for an image time series from savery creek wyoming usa and to evaluate various transformation equations interpolation methods and gcp placement strategies interpolated error surfaces then were used to create error ellipses representing spatially variable buffers of detectable change our results show that for all five sequential image pairs we examined spatially distributed estimates of registration error enabled detection of a greater number of statistically significant lateral migration vectors than the spatially uniform rmse or 90th percentile of gcp error conversely spatially distributed error metrics prevented changes from being mistaken as real in areas of greater registration error our results also support the findings of previous studies second order polynomial functions on average yield the lowest rmse and errors are reduced by placing gcps on the floodplain rather than on hillslopes this study highlights the importance of characterizing the spatial distribution of image registration errors in the analysis of channel change

on lagrangian residual currents with applications in south san francisco bay california the lagrangian residual circulation has often been introduced as the sum of the eulerian residual circulation and the stokes drift unfortunately this definition of the lagrangian residual circulation is conceptually incorrect because both the eulerian residual circulation and the stokes drift are eulerian variables in this paper a classification of various residual variables are reviewed and properly defined the lagrangian residual circulation is then studied by means of a two stage formulation of a computer model the tidal circulation is first computed in a conventional eulerian way and then the lagrangian residual circulation is determined by a method patterned after the method of markers and cells to demonstrate properties of the lagrangian residual circulation application of this approach in south san francisco bay california is considered with the aid of the model results properties of the eulerian and lagrangian residual circulation are examined it can be concluded that estimation of the lagrangian residual circulation from eulerian data may lead to unacceptable error particularly in a tidal estuary where the tidal excursion is of the same order of magnitude as the length scale of the basin a direction calculation of the lagrangian residual circulation must be made and has been shown to be feasible

new insights on the sorbas basin se spain the onshore reference of the messinian salinity crisis the sorbas basin is the land reference of the messinian salinity crisis msc that affected the mediterranean sea in the latest miocene its stratigraphy has been re visited using calcareous nannofossils and planktonic foraminifers which provide a reliable biostratigraphic frame and lead to particularly specify the relationships between the sorbas and zorreras members with yesares evaporites the evaporites overlie a shallowing upward sequence ending with the deposition of the reef unit and terminal carbonate complex tcc on the periphery of the basin the reefal carbonates of the tcc are overlain by clastic deposits that are foreset beds of post msc gilbert type fan deltas developed on the northern edge of the basin these sedimentary structures are separated from reefal carbonates and the reef unit by the messinian erosional surface mes the various facies of the sorbas member have been correlated with the bottomset beds of the gilbert type fan deltas despite some differences in palaeobathymetry in the southeastern periphery of the basin the mes separates the sorbas member from the yesares gypsums in the central part of the basin a hiatus characterizes the contact between these members the zorreras member postdates the msc and entirely belongs to zanclean its white lago mare layers are lagoonal deposits the fauna of which is confirmed to result from mediterranean paratethys high sea level exchange after the post msc marine reflooding of the mediterranean basin this study allows to re assert the two step scenario of the msc clauzon et al 1996 with the following events at 5 971 5 600 ma minor sea level fall resulting in the desiccation of this peripheral basin with secondary fluctuations at 5 600 5 460 ma significant subaerial erosion or lack of sedimentation caused by the almost complete desiccation of the mediterranean sea instantaneous marine reflooding accepted at 5 460 ma followed by continuing sea level rise

episodes of vertical accretion and catastrophic stripping a model of disequilibrium flood plain development this paper describes flood plains formed episodically by vertical accretion along high energy laterally stable channels in southeastern australia overbank deposition gradually builds a flood plain of fine textured alluvium over a period of hundreds or thousands of years following which catastrophic erosion by a single large flood or a series of more moderate floods strips the flood plain to a basal lag deposit from which it slowly reforms this periodic destruction appears due to the progressive development of large levee banks and flood plain surfaces of highly variable relief as the levees and flood plain grow overbank flow is gradually displaced from the broad flood plain into the main channel and flood plain backchannels with a resulting concentration of erosional energy eventually high flows greatly exceed erosional thresholds and wholesale scour of the channel boundary and flood plain occurs vertical accretion flood plains at different stages of development result in a wide range of bankfull recurrence intervals even along the same river some of these flood plains are so infrequently flooded that they can be mistaken for terraces formed under a prior flow regime the almost random but catastrophic nature of this flood plain erosion means that sediment supply and transport are highly variable and probably impossible to predict this model of flood plain formation is seen as only part of a continuum of alluvial environments ranging from vestigial coarsegrained traction load flood plains along high energy rivers in narrow gorges to extensive low gradient flood plains in which alluvial stratigraphy is dominated by fine grained overbank deposition

carbonate ramp depositional systems abstract the classification tectonic settings stratigraphy and early diagenesis of carbonate ramp systems are reviewed carbonate ramps are common in all geological periods but were dominant at times when reef constructing organisms were absent or inhibited ramps can be subdivided into inner mid and outer ramp environments the mid ramp zone extends from fair weather wave base to normal storm wave base although the water depths which these boundaries represent vary an additional outer slope environment occurs on distally steepened ramps as with siliciclastic shelves a range of wave storm and tide dominated ramps can be recognised and this forms the most convenient basis for ramp classification the carbonate productivity profile of ramps differs from that of rimmed shelves with the inner ramp showing lower production rates than comparable shallow water facies on rimmed shelves the zone of greatest organic carbonate sediment production appears to have shifted from the mid ramp to the inner ramp since the late jurassic carbonate ramps occur in most types of sedimentary basin but are best developed where subsidence is flexural and gradients are slight over large areas as in foreland and cratonic interior basins and along passive margins the featureless depositional profiles of many ramps means that sequence geometries are best observed on regional seismic lines some show low angle sigmoidal or shingled clinoforms suggesting that ramps may seldom be homoclinal but possess subtle slope geometries which reflect depositional environments because of their low angle slopes ramps respond differently to rimmed shelves during relative sea level changes although results seem to be strongly dependent on the rate of relative sea level change during a minor fall shallow ramp facies belts will simply shift basinwards in a forced regression in contrast the whole surface of a steep sloped flat topped rimmed shelf may be exposed so that sediment production ceases or is drastically reduced during a major fall shallow ramp bounded basins may empty completely conversely ramps also flood gradually whereas rimmed shelves do so more rapidly homoclinal ramps develop no resedimented lowstand deposits rimmed shelves and distally steepened ramps in contrast may develop lowstand talus or turbiditic wedges distally steepened ramps may behave more like homoclinal ramps during minor base level falls and like rimmed shelves during major base level falls many ramps consist of layered successions of several ramp sequences stacked one upon the other ramp stacks of this sort may show gross vertical accretion but individual ramp sequences seldom appear to develop in a keep up style apart from minor organic buildups as with many rimmed shelves steepening of the outer ramp margin due to tectonism slope inheritance or differential sedimentation may promote the development of a distally steepened ramp or rimmed shelf a wide variety of organisms have constructed buildups in mid and outer ramp environments isolated buildups may seed early in ramp development accrete to wave base or sea level and continue growth by stacking through successive ramp sequences so that depositional and diagenetic features within them are in concert with those of the shallow ramp the location of isolated buildups on ramps is governed by tectonism halokinesis antecedent topography or by the subtle slope geometry of the previous ramp sequence diagenesis on ramps shows some major variations compared with diagenesis on steep sloped flat topped carbonate platforms ramp bounded basins may form prolific petroleum sourcing and reservoiring systems and offer a range of subtle stratigraphic play types and lateral facies variations which determine reservoir quality and distribution isolated buildups in the mid and outer ramp environments represent one of the commonest petroleum reservoirs in ramp systems and tend to have their foundations in transgressive systems tracts grainstone and packstone reservoirs are widespread and range from shoreline carbonate sandbodies to major detached shoal complexes or shoals over offshore highs grainstone sandbodies occur in both highstand systems tracts and in prograding lowstand wedges

testing models for the messinian salinity crisis the messinian record in almeria se spain abstract neogene intermontane basins in almeria province se spain display excellent exposures of messinian late miocene sequences the sorbas almeria nijar and vera basins maintained connection with the mediterranean throughout the messinian except during the major desiccation phase leading to the formation of salt in the deep centre of the western mediterranean these basins were part of the western mediterranean with no separate link to the atlantic ocean the presence of normal marine sediments in these basins reflects the western mediterranean watermass messinian pre evaporitic sediments in the basins of southeastern almeria do not show gradual change towards evaporite deposits instead they contain stenohaline invertebrates right up to a major erosion surface that separates them from overlying gypsum deposits this contradicts suggestion of progressive salinity increase in this part of the western mediterranean prior to the messinian salinity crisis msc it also indicates that initiation of evaporite precipitation was not synchronous throughout the mediterranean basin there is no major erosion surface within or at the top of the evaporites in these almeria basins and the gypsum beds exhibit upward transition to siliciclastic and carbonate deposits this is inconsistent with a model of messinian mediterranean evaporite formation whereby deposition of marginal evaporites was followed by their erosion during drawdown that resulted in formation of evaporites in the centre of the western mediterranean the presence of stenohaline biotas in siliciclastic deposits interbedded with the gypsum and in the messinian post evaporitic sediments challenges the view that a long standing large body of brackish water the lago mare filled the western mediterranean following the msc and prior to early pliocene flooding it also contradicts the concept of many relatively small brackish basins spread across an otherwise desiccated western mediterranean basin the basins of southeastern almeria record normal marine early messinian sedimentation that was abruptly interrupted by sealevel fall this drawdown most likely resulted in precipitation of evaporites in the central deep western mediterranean basin following this episode final marine reflooding of the western mediterranean took place during the late messinian and the mediterranean sea rose to a level similar to or higher than that preceding the salinity crisis

flow reconstructions in the upper missouri river basin using riparian tree rings river flow reconstructions are typically developed using tree rings from montane conifers that cannot reflect flow regulation or hydrologic inputs from the lower portions of a watershed incorporating lowland riparian trees may improve the accuracy of flow reconstructions when these trees are physically linked to the alluvial water table we used riparian plains cottonwoods populus deltoides ssp monilifera to reconstruct discharge for three neighboring rivers in the upper missouri river basin the yellowstone n 389 tree cores powder n 408 and little missouri rivers n 643 we used the regional curve standardization approach to reconstruct log transformed discharge over the four months in early summer that most highly correlated to tree ring growth the reconstructions explained at least 57 of the variance in historical discharge and extended back to 1742 1729 and 1643 these are the first flow reconstructions for the lower yellowstone and powder rivers and they are the furthest downstream among rocky mountain rivers in the missouri river basin although mostly free flowing the yellowstone and powder rivers experienced a shift from early to late summer flows within the last century this shift is concurrent with increasing irrigation and reservoir storage and it corresponds to decreased cottonwood growth low frequency flow patterns revealed wet conditions from 1870 1980 a period that includes the majority of the historical record the 1816 1823 and 1861 1865 droughts were more severe than any recorded revealing that drought risks are underestimated when using the instrumental record alone this article is protected by copyright all rights reserved

the messinian salinity crisis past and future of a great challenge for marine sciences forty years after the image of the mediterranean transformed into a giant salty lake was first conceived the fascinating history of the messinian salinity crisis msc still arouses great interest across a large and diverse scientific community early outcrop studies which identified severe palaeoenvironmental changes affecting the circum mediterranean at the end of the miocene were followed by investigations of the marine geology during the 1950s to 1970s these were fundamental to understanding the true scale and importance of the messinian event now after a long period of debate over several entrenched but largely untested hypotheses a unifying stratigraphic framework of msc events has been constructed this scenario is derived mainly from onshore data and observations but incorporates different perspectives for the offshore and provides hypotheses that can be tested by drilling the deep mediterranean basins the msc was an ecological crisis induced by a powerful combination of geodynamic and climatic drivers which had a great impact on the subsequent geological history of the mediterranean area and on the salinity of the global oceans these changed the mediterranean s connections with both the atlantic ocean and the freshwater paratethyan basins causing high amplitude fluctuations in the hydrology of the mediterranean the msc developed in three main stages each of them characterized by different palaeoenvironmental conditions during the first stage evaporites precipitated in shallow sub basins the msc peaked in the second stage when evaporite precipitation shifted to the deepest depocentres and the third stage was characterized by large scale environmental fluctuations in a mediterranean transformed into a brackish water lake the very high resolution timescale available for some late miocene intervals in the mediterranean makes it possible to consider environmental variability on extremely short time scales including in some places annual changes despite this fundamental questions remain some of which could be answered through new cores from the deepest mediterranean basins improvements in seismic imaging and drilling techniques over the last few decades make it possible to plan to core the entire basinal messinian succession for the first time the resulting data would allow us to decipher the causes of this extreme environmental change and its global scale consequences

underground riparian wood buried stem and coarse root structures of black poplar populus nigra l abstract despite the potential importance of tree species in influencing the processes of wood recruitment transport retention and decay that control river wood budgets focus has been relatively limited on this theme within fluvial wood research furthermore one of the least investigated topics is the belowground living wood component of riparian trees this paper presents observations of the morphology and age of buried stem and coarse root structures of eight populus nigra individuals located in the riparian woodland of two sites on the middle to lower tagliamento river italy this species was selected because of its wide distribution along european rivers and its frequent dominance of riparian woodland each tree was excavated by hand to expose a minimum of half of the root system with complete exposure of the main axis smaller roots were then removed and larger protruding roots cut back to permit access to the main axis the excavated structures were photographed from multiple angles for photogrammetric modelling the structure and character of the exposed sediments around the tree s main axis were recorded and wood samples were taken from the main aboveground stem s sections of the main buried axis and major roots for dendrochronological analysis results from these field observations and laboratory dating of the wood samples were combined to describe the belowground morphology of each tree and to draw inferences concerning the impact of fluvial disturbances common features of these excavated structures included i rooting depths to below the bar surface where the original tree established with many young roots also existing at depth ii translocation of the main buried axis in a downstream direction iii a main buried axis comprised mainly of stems that have become buried and then generated new shoots including multistem patches and adventitious roots iv the presence of steps and bends in the main buried axis associated with the generation of coarse lateral roots that reflect the sedimentary structure of the surrounding aggraded bank sediments and v grafting of roots within and between some sampled trees overall the sampled trees possessed extremely complex three dimensional buried wood structures that permeate bank sediments and tie the tree and aggraded bank sediments to basal gravels these properties and the considerable amount of underground wood that is present have great significance for anchoring trees and giving uprooted trees and root wads a propensity to snag once they enter the fluvial system furthermore the ability of this underground biomass to sprout suggests that uprooted and remaining components of root networks following tree uprooting may resprout generating new vegetation canopies that can trap mobile wood overall this underground wood offers many traits that may tighten wood budgets and it is likely that other riparian salicaceae species with similar traits may have similar wood budget impacts

application of three dimensional lagrangian residual transport three dimensional lagrangian residual circulation computed from an intratidal hydrodynamic model is used to drive an intertidal water quality transport model the sum of the eulerian residual and stokes drift is used as a first order approximation for the lagrangian residual current the stokes drift approximates residual currents induced by the nonlinear interactions of the tidal currents computed residual velocities show close agreement with a two dimensional vertical longitudinal analytical result the methodology is applied to chesapeake bay for the entire year of 1985 salinity computed with the intertidal transport model i e with lagrangian residuals shows good agreement with observed salinity data and that computed with the intratidal hydrodynamic model the basic effect of the stokes drift is to transport water mass e g salinity up estuary the procedures provide a practical means of interfacing intratidal hydrodynamic model information to water quality models for making long term in

late miocene halimeda alga microbial segment reefs in the marginal mediterranean sorbas basin spain a 6 ma messinian late miocene bioherm unit on the southern slope of the sorbas basin se spain contains numerous biotically diverse lensoid patch reefs that formed on a shelf to basin slope during a cycle of relative sea level change halimeda reefs are the largest and most complex of the patch reefs and are divisible into core cap and flank facies on the upper and midslope they are up to 40 m thick and 400 m long they become smaller downslope the core consists of jumbled halimeda segments released by spontaneous disaggregation of the alga the segments were stabilized close to their sites of growth and rapidly lithified by micritic and peloidal microbial crusts residual cavities were further veneered by isopachous marine cements flank facies consisting of bedded packstones to rudstones form wedge shaped units lateral to the mounds cap facies consist of bioclastic calcarenites calcirudites and microbial carbonates synsedimentary lithification assisted rapid accretion and inhibited off mound export of sediment allochthonous reef derived blocks on the mid slope reflect penecontemporaneous rigidity of the halimeda bioherms proximal porites coral frame patch reefs associated with calcarenites were located near the shelf margin during the initial lowstand stage halimeda segment reefs associated with calcarenites and silty marls developed on the midslope and bivalve bryozoan serpulid reefs formed on the lower slope in silty marls with occasional turbidites during the transgressive stage coral patch reefs near the shelfbreak were overgrown by halimeda during highstand progradation cap facies spread basinward as a sheet connecting many of the midslope patch reefs these ancient analogues differ from most modern halimeda reefs in being discrete laterally restricted patch reefs surrounded by marly sediment and located on a slope they are however broadly comparable in biota thickness and depositional depth intense early lithification by microbial crusts and marine cements is an important feature of these messinian segment reefs it has not been reported from modern examples

a new view of near shore dynamics based on observations from hf radar abstract since 1984 the oscr hf radar system has been used in over 50 deployments to measure near shore surface currents for both scientific and engineering applications the enhanced scope resolution and accuracy of these measurements have yielded new insights into the tidal wind and density driven dynamics of the near shore zone tidal current ellipses obtained from these radar measurements have been shown to be in good aggrement with values calculated by numerical models both for the predominant constituents and also for higher harmonics coherent patterns of wind forced currents ahve been determined with strong evidence of a slab like surface response in one deployment with offshore winds blowing over relatively deep water this slab rotated clockwise at near inertial frequency strong up to 20cm s 1 persistent surface residual currents are commonly observed these are almost certainly generated by small horizontal density gradients these observed surface residuals provide ideal data for rigorous testing of 3 d numerical models with a threatened rise in sea level hf radar is well suited for observing the expected changes in the dynamics of near shore regions continuing development of these radar systems offers exciting prospects of remote sensing of both surface waves and currents future applications may extend beyond the near shore region to measurements along the shelf edge in oceanic gyres and for beach processes

chronology causes and progression of the messinian salinity crisis the messinian salinity crisis is widely regarded as one of the most dramatic episodes of oceanic change of the past 20 or so million years 1 3 earliest explanations were that extremely thick evaporites were deposited in a deep and desiccated mediterranean basin that had been repeatedly isolated from the atlantic ocean1 2 but elucidation of the causes of the isolation whether driven largely by glacio eustatic or tectonic processes have been hampered by the absence of an accurate time frame here we present an astronomically calibrated chronology for the mediterranean messinian age based on an integrated high resolution stratigraphy and tuning of sedimentary cycle patterns to variations in the earth s orbital parameters we show that the onset of the messinian salinity crisis is synchronous over the entire mediterranean basin dated at 5 96 0 02 million years ago isolation from the atlantic ocean was established between 5 59 and 5 33 million years ago causing a large fall in mediterranean water level followed by erosion 5 59 5 50 million years ago and deposition 5 50 5 33 million years ago of non marine sediments in a large lago mare lake sea basin cyclic evaporite deposition is almost entirely related to circum mediterranean climate changes driven by changes in the earth s precession and not to obliquity induced glacio eustatic sea level changes we argue in favour of a dominantly tectonic origin for the messinian salinity crisis although its exact timing may well have been controlled by the 400 kyr component of the earth s eccentricity cycle

the primary lower gypsum in the mediterranean a new facies interpretation for the first stage of the messinian salinity crisis abstract the detailed facies and physical stratigraphic analysis of the primary lower gypsum in the mediterranean indicates a surprising bed by bed correlation at basin scale spain italy hellenic arc and cyprus arc that is tuned to the orbital calibration for the first stage of the messinian salinity crisis from 5 96 to 5 61 ma ago a total of 16 precessionally controlled gypsum cycles were deposited rapidly in less than 350 ka forming sequences up to 300 m thick the lack of subaerial exposure features and the common facies associations and stacking pattern for sections located thousands of kilometers apart in different geological settings indicates a modest depositional depth not extremely shallow selenite deposition occurred only at the bottom of restricted marginal basins less than 200 m deep while no gypsum could precipitate in the deeper euxinic mediterranean portions where only thin and barren shale dolostone couplets formed the lowermost selenite beds pass laterally to dolomite rich limestones interbedded with barren euxinic shales in poorly oxygenated settings indicating that the gypsum sedimentation was diachronous and did not necessarily mark the onset on the messinian salinity crisis evaporite facies sequences ef1 to 8 within individual gypsum beds show small scale subaqueous sedimentary cycles that mimic regressive transgressive cycles a initial evaporite precipitation at relatively low supersaturation produced the massive selenite facies ef3 in a relatively deep setting b continuous evaporation and drawdown by oscillating brine level formed the banded selenite ef4 at the aridity acme of the precessionally controlled cycle c general progressive brine level rise with strong brine flow led to the formation of large selenite supercones branching laterally supercones in spain and branching selenite ef5 in the rest of the mediterranean and d flooding by undersaturated continental water terminated gypsum precipitation with the deposition of argillaceous sediments ef1 northern apennines and or limestone ef2 sicily and spain during the humid phase in the precession climate cycle the stacking pattern and selenite facies associations suggest an overall shallowing upward trend with a basin wide hydrologic change starting from the 6th cycle 5 84 ma which is marked by the appearance of the branching selenite facies supercones in spain and indicates that the brines became current dominated the sr isotope stratigraphy suggests that in the northern apennines the brines were strongly modified by continental waters 87 sr 86 sr 0 708893 to 0 708998 and received direct pulses of atlantic seawater 87 sr 86 sr 0 70900 to 0 709024 only in the upper part of the section in areas away from the mainland such as sicily the continental input was by far less important

floodplain dynamics of a wandering river dendrochronology of the morice river british columbia canada dendrochronological techniques are used to develop a history of flood occurrence and relative stage for the middle section of the morice river based on flood scars bank undercutting dates and tree establishment dates on fluvial features the morice river is the major tributary of the bulkley river skeena river system northwest british columbia canada reach 2 of the morice river drainage area 3499 km2 is forested and little disturbed by human activity it is presently a wandering multiple channel river and shows evidence of frequent channel changes which have reworked most of the floodplain several times in the last 180 years airphoto analysis and dendrochronology demonstrate that many channels show evidence of two or more periods of activity reoccupation and re excavation of pre existing channel segments is more frequent than development of new channels thirty one significant floods over the past 105 years were detected through dendrochronology of flood scarred trees on the morice river flood scars are predominantly caused by flood transported logs abundant log transport results in damage to channel margin trees during events only slightly above bankfull discharge the record of flood scars on channel margin trees and establishment dates of forest stands on abandoned channels and surfaces show that the morice river has maintained its present regimen for the past 115 years during the neoglacial the morice river was more active than in recent times and its channels occupied twice the present area tree establishment dates show that neoglacial surfaces and channels of the morice river were abandoned during the 1820 s the modern floodplain configuration was assumed by 1870

messinian salinity crisis a novel unifying shallow gypsum deep dolomite formation mechanism abstract the messinian salinity crisis is a dramatic event that took place between 5 96 and 5 33 ma and resulted not only in the desiccation and reflooding of the mediterranean but also in the deposition of 0 3 3 km thick evaporites at its seafloor there has been considerable controversy on the modes of their formation the first stage gypsum deposits are considered to have only formed at silled marginal basins whereas anoxic marls and dolostones are found at deeper settings we agree with these observations but reject the coincidental presence of similar sills as being too fortuitous to explain gypsum formation in silled basins alone alternatively we present a unifying mechanism in which gypsum precipitation takes place basin wide at all shallow water depths but its preservation is limited to silled marginal basins taking a realistic early messinian scenario including a moderate primary production rate the sulphate consumption rate in the deep water appears to exceed the sulphate supply rate as deduced from reported shallow water gypsum deposition rates the consequent lower dissolved sulphate content limits gypsum preservation but permits dolomite formation to take place in the deep water the often observed concurring anoxic environment and absence of gypsum formation is thus related to diminished dissolved sulphate content via organic matter degradation and not to oxygen free conditions as such

palaeoceanographic controls on reef deposition the messinian cariatiz reef sorbas basin almeria se spain abstract the cariatiz section lies at the toe of the palaeoslope of the messinian cariatizfringing reef at the northern margin of the neogene sorbas basin in se spain distal slope reef deposits in the upper part of the section can be traced laterallyto the reef core of the last episodes of reef progradation the underlyingdeposits are alternating diatomitic marl marl and silty marl that intercalatewith sandstone beds combined lithological changes variations in proportionsof warm water planktic foraminifera and d18o values suggest that at leastseven probably precessional cycles are recorded throughout the cariatizsection the correlation of seven cycles in the pelagic deposits to seven reefprogradation cycles and associated vertical shifts in reef facies indicatesrelative sea level oscillations of several tens of metres biostratigraphic andpalaeomagnetic data suggest that both the cariatiz section and the fringing reefformed during the reverse polarity chron c3r surface water temperaturesseem to be the major factor controlling carbonate production in the reef system deposition of bioclastic calcirudite and calcarenite with no active coralgrowth took place at the lowest sea level within each reef cycle duringtemperature minima within each precessional cycle porites framework andreef slope deposits with halimeda gravel in contrast formed duringtemperature rises and thermal maxima within precessional cycles keywords messinian palaeoceanography planktic foraminifera reef car bonates sorbas basin stable isotopes introductiona number of palaeoceanographic studies havebeen carried out on the messinian pre evaporiticdeposits from the mediterranean region i e vergnaud grazzini 1985 benson et al 1991 krijgsman et al 1999a blanc valleron et al 2002 sierro et al 2003 stable isotope micro palaeontological and sedimentary records indi cate varying degrees of restriction of themediterranean sea from the atlantic before theonset of the messinian salinity crisis and stressthe cyclic nature of changes in hydrographicconditions speci cally oscillations in the com position of microfossil assemblages lithology andstable isotope signals re ect climatic cyclityforced by precession sprovieri et al 1996 blanc valleron et al 2002 sierro et al 2003 in addition many reports have dealt with thestratigraphic and palaeogeographic distribution structure and composition of messinian coralreefs that developed at the margins of mediterra nean basins dabrio et al 1981 pomar 1991 riding et al 1991 braga marti n 1996 estebanet al 1996 up to now however the relation ships between the environmental changes recor ded in the reef carbonates and those re ected inequivalent pelagic deposits have been poorlysedimentology 2007 54 637 660

estuarine salt conservation a lagrangian approach abstract understanding tidal and mean flow transport mechanisms that maintain the estuarine salt balance against seaward transport by river flow is one of the fundamental questions of estuarine oceanography previous salt transport studies have failed to resolve this problem for two principal methodological reasons in addition to the inherent variability of estuaries first salt transport expansions used to represent the salt balance have included a large number of terms that could not be related to any theory of estuarine circulation and whose physical meaning was thus unclear second it has proven difficult to measure small mean velocities in the presence of much larger tidal variations a new analysis method that expresses lagrangian scalar property transport in terms of time and space variations of eulerian variables is much simpler than expansions previously used and yields new insights into estuarine transport processes this approach like previous expansions is valid for narrow systems in which cross channel transport processes are weak and the ratio of tidal amplitude to mean depth is small a surface boundary condition is used to eliminate one class of troublesome terms the equivalence of the tidal cycle average transport of tidal variations in salinity and the stokes transport of mean salinity is then employed to show that the vertically integrated tidal flow plays no role in the overall salt balance that is seaward transport of salt caused by the river flow can only be balanced by landward transport resulting from correlations between shear and stratification in the mean tidal and overtide flows in a hypothetical inviscid estuary tide and overtide flows would be vertically uniform and outward fluvial salt transport could only be balanced by shear and stratification in the mean gravitational circulation in a more realistic example with strong friction the gravitational circulation would be severely damped and inward transport could only be accomplished by correlations of shear and stratification in the tide and overtide flows

orbitally controlled oscillations in planktic communities and cyclic changes in western mediterranean hydrography during the messinian we use quantitative analyses of the planktic foraminiferal assemblages and stable isotope analyses of the sorbas section in the western mediterranean to reconstruct the cyclical changes in surface and deep water hydrographic conditions during the late miocene prior to the messinian salinity crisis oscillations in winter and summer temperatures linked to cyclical fluctuations in the hydrographic conditions and nutrient availability were the main mechanisms driving the cyclical changes in the planktic foraminiferal assemblages during the messinian the winter intensification and southward expansion of the northern cool and dry winds during precession maxima lowered sea surface temperatures below 14 15 c favoring water convection and the upward mixing of nutrients with the consequent increase in the proportion of cold eutrophic water foraminifera the low summer temperatures below 24 c inhibited the growth of warm oligotrophic water foraminifera as occurs today in the mediterranean by contrast at times of precession minima the low influence of the high latitude air masses caused winter temperatures to remain relatively high which combined with the lower surface salinities led to the formation of a permanent pycnocline winter conditions prevented the growth of cold eutrophic water foraminifera while high summer temperatures and the formation of a permanent pycnocline stimulated the growth of warm oligotrophic water foraminifera the prevalence of stable water stratification during winter due to the large density gradient between the surface and intermediate waters prevented deep water formation and slowed down the rates of oxygen supply to the bottom resulting in the formation of the sapropels a sharp decrease in 13c of benthic and planktic foraminifera that occurred between 6 8 and 6 7 myr is related to an increase in the residence time of mediterranean waters because similar changes have been observed in other regions of the mediterranean we conclude that this change records a significant reduction in the atlantic mediterranean water exchange at that time mediterranean climatic amplification increased throughout the messinian as the atlantic mediterranean water exchange was progressively more limited and oscillations in the ratio of planktic benthic foraminifera and of warm oligotrophic cold eutrophic species are good records of this increasing amplification which culminated at 5 95 myr with the deposition of gypsum pelitic layers that mark the onset of the messinian salinity crisis

classification of geomorphological effects downstream of dams abstract the effects of dams on downstream geomorphology are reviewed and a typology is devised consisting of nine cases the classification can be seen as a further development of lane s balance between water discharge sediment load grain size and river slope depending on changes in released water flow and changes in released sediment load relative to the transport capacity of the flow it is possible to estimate resulting cross sectional geomorphology the longitudinal extent of changes and their variability with time and the tributary response to altered mainstream cross section changes are also discussed

downstream patterns of suspended sediment transport in a high arctic river influenced by permafrost disturbance and recent climate change abstract spatially and temporally variable suspended sediment transport from upstream sources was investigated in the west river unofficial name at the cape bounty arctic watershed observatory cbawo on melville island nunavut 74 55 n 109 35 w a river with nearly a decade of hydrological and sediment transport research in the canadian arctic and subject to recent permafrost disturbances such as soil skin flows on slopes massive ground ice melt in the channel and substantial climate change during the 2012 season a survey was undertaken during the nival period to identify areas of the river where the flow was isolated from the channel bed by snow and where it progressively reached the bed during the nival period and throughout the rest of the season suspended sediment transport data were collected from a primary outlet station and six upstream locations to identify the sources and sinks of sediment in the various reaches of the west river an inferred sediment budget approach was used to identify the storage and release dynamics in each reach nival event scale hysteresis and seasonal diurnal hysteresis patterns for 2012 were primarily anticlockwise suggesting that sources of sediment were not readily available for transport during peak flows but became available as discharge waned analysis of diurnal hysteresis relationships for the years 2004 2012 excluding 2011 signals a shift in daily sediment discharge hysteresis from primarily clockwise to anticlockwise following an episode of permafrost disturbance and enhanced erosion in 2007 consistent sediment storage in the upper catchment from this disturbance is interpreted to have contributed to the shift to anticlockwise daily hysteresis results provide insights into the fluvial and geomorphological response to changes in sediment availability in arctic rivers and how these changes in turn affect sediment transport in these environments

synchronous onset of the messinian evaporite precipitation first mediterranean offshore evidence the messinian salinity crisis msc was a major ecological crisis affecting shallow and deep water settings over the entire mediterranean basin however the evolution of the msc and its ecological impacts have mainly been explained on the basis of sediments from onshore outcrops lack of complete and physically connected records from onshore and offshore settings has inhibited comprehensive understanding of basin behaviour during the msc herein we present a continuous record from an intermediate depth basin on the balearic promontory that comprises late tortonian messinian marls and evaporitic beds from the first msc phase i e primary lower gypsum plg stage well log and biostratigraphic data allow us establishing a large scale calibration to the astronomical solutions and to correlate pre msc sediments with classical rhythmic successions outcropping onshore thickness and characteristic sedimentary patterns observed in the offshore evaporitic records resemble those from marginal plg sequences furthermore seismic reflectors from a bedded unit bu which corresponds to an evaporitic interval according to well to seismic ties are correlated with the onshore plg sequences this correlation constitutes the first attempt to link well known marginal sequences with intermediate depth offshore settings which have previously only been studied through seismic imaging our time calibration provides direct evidence supporting a synchronous onset of the plg phase between onshore and offshore settings along the southwestern balearic promontory margin those bu reflectors which were positively correlated to the plg were likely precipitated offshore the continental shelf at messinian times these results suggest that gypsum precipitation and or preservation was not always limited to 200 m water depths and could occur in non silled basins finally we only found a major erosion at the top of the plg sequences implying that the msc drawdown occurred after the precipitation of the onshore lower evaporites studied sequences provide new insights into the plg precipitation preservation settings as well as into the land sea correlations of msc units and thus could potentially help refine current msc models

late miocene mediterranean desiccation topography and significance of the salinity crisis erosion surface on land in southeast spain reply abstract the result of sea level fall at the margins of the mediterranean during the late miocene salinity crisis was the creation of an extensive erosion surface however the shape of this salinity crisis unconformity reflects local factors and in turn significantly determined local conditions during subsequent reflooding at sorbas in southeast spain erosional overdeepening of a pre existing basin during drawdown created a depression over 200 m deep with an incised floor patterned by 30 m deep gullies during reflooding this semi enclosed palaeovalley temporarily became a barred basin in which gypsum was deposited these sorbas evaporites thus resulted from local basin sculpture diverse local effects elsewhere during drawdown and reflooding account for marked stratigraphic variations that continue to complicate recognition and correlation of the salinity crisis in marginal successions the drawdown erosion surface is itself the key indicator of this important event in marginal mediterranean basins

a signature of transience in bedrock river incision rates over timescales of 10 4 10 7 years measured rates of river incision into bedrock are commonly interpreted as proxies for rates of rock uplift see refs 1 and 2 for example and indices of the strength of climatic forcing of erosion over time see refs 3 and 4 for example this approach implicitly assumes that river incision rates are in equilibrium with external forcings over a wide range of timescales here we directly test this assumption by examining the temporal scaling of bedrock river incision from 155 independent measurements of river incision compiled from 14 sites of these sites 11 exhibit a negative power law dependence of bedrock river incision rate on measurement interval a relationship that is apparent over timescales of 10 4 10 7 years and is independent of tectonic and geomorphic setting thus like rates of sediment accumulation rates of river incision into bedrock exhibit non steady state behaviour even over very long measurement intervals non steady state behaviour can be explained by episodic hiatuses in river incision triggered by alluvial deposition if such hiatuses have a heavy tailed length distribution regardless of its cause the dependence of incision rate on measurement interval complicates efforts to infer tectonic or climatic forcing from changes in rates of river incision over time or from comparison of rates computed over different timescales

ontogeny of a flood plain the ontogeny of five flood plain segments is described for a period of 18 yr following a major flood in 1978 on the powder river in southeastern montana the flood plains developed on relatively elevated sand and gravel deposits left within the channel by the 1978 flood in cross section the flood plains resemble benches with well developed natural levees flood plain growth occurred as sediment was draped onto preexisting surfaces in layers of sand and mud a few centimeters to decimeters thick resulting in some lateral but mostly vertical accretion annual and biannual measurements indicated that as the flood plain segments grew upward the annual rate of vertical accretion decreased as the partial duration recurrence interval for the threshold or bankfull discharge increased from 0 16 to 1 3 yr it is clear that a constant recurrence interval for overbank flow cannot be meaningfully assigned to this type of flood plain ontogeny these flood plains did not grow on migrating point bars and vertical accretion at least initially occurred within the channel rather than across the valley flat during extensive overbank flows sediments of these flood plains define narrow elongated stratigraphic units that border the active channel and onlap older flood plain deposits these characteristics are considerably different from those of many facies models for meandering river deposits facies similar to those described in this paper are likely to be preserved thereby providing important evidence in the geologic record for episodes of periodic channel expansion by ancient rivers

influence of flow variability on floodplain formation and destruction little missouri river north dakota resolving observations of channel change into separate planimetric measurements of floodplain formation and destruction reveals distinct relations between these processes and the flow regime we analyzed a time sequence of eight bottomland images from 1939 to 2003 along the little missouri river north dakota to relate geomorphic floodplain change to flow along this largely unregulated river at the decadal scale floodplain formation and destruction varied independently destruction was strongly positively correlated with the magnitude of infrequent high flows that recur every 5 10 yr whereas floodplain formation was negatively correlated with the magnitude of frequent low flows exceeded 80 of the time at the century scale however a climatically induced decrease in peak flows has reduced the destruction rate limiting the area made available for floodplain formation the rate of destruction was not uniform across the floodplain younger surfaces were consistently destroyed at a higher rate than older surfaces suggesting that throughput of contaminants would have occurred more rapidly than predicted by models that assume uniform residence time of sediment across the floodplain maps of floodplain ages produced by analysis of sequential floodplain images are similar to maps of forest ages produced through dendrochronology confirming the assumption of dendrogeomorphic studies that riparian tree establishment in this system is limited to recent channel locations

paratethys pacing of the messinian salinity crisis low salinity waters contributing to gypsum precipitation during the so called messinian salinity crisis msc 5 97 5 33 myr ago reduced exchange with the atlantic ocean caused the mediterranean to develop into a saline giant wherein 1 million km3 of evaporites gypsum and halite were deposited despite decades of research it is still poorly understood exactly how and where in the water column these evaporites formed gypsum formation commonly requires enhanced dry conditions evaporation exceeding precipitation but recent studies also suggested major freshwater inputs into the mediterranean during msc gypsum formation here we use strontium isotope ratios of ostracods to show that low saline water from the paratethys seas actually contributed to the precipitation of mediterranean evaporites this apparent paradox urges for an alternative mechanism underlying gypsum precipitation we propose that paratethys inflow would enhance stratification in the mediterranean and result in a low salinity surface water layer with high ca cl and so4 cl ratios we show that evaporation of this surface water can become saturated in gypsum at a salinity of 40 in line with salinities reported from fluid inclusions in msc evaporites

on tide induced lagrangian residual current and residual transport 2 residual transport with application in south san francisco bay california the transports of solutes and other tracers are fundamental to estuarine processes the apparent transport mechanisms are convection by tidal current and current induced shear effect dispersion for processes which take place in a time period of the order of a tidal cycle however as emphasis is shifted toward the effects of intertidal processes the net transport is mainly determined by tide induced residual circulation and by residual circulation due to other processes the commonly used intertidal conservation equation takes the form of a convection dispersion equation in which the convective velocity is the eulerian residual current and the dispersion terms are often referred to as the phase effect dispersion or sometimes as the tidal dispersion the presence of these dispersion terms is merely the result of a fickian type hypothesis since the actual processes are not fickian thus a fickian hypothesis obscures the physical significance of this equation recent research results on residual circulation have suggested that long term transport phenomena are closely related to the lagrangian residual current or the lagrangian residual transport in this paper a new formulation of an intertidal conservation equation is presented and examined in detail in a weakly nonlinear tidal estuary the resultant intertidal transport equation also takes the form of a convection dispersion equation without the ad hoc introduction of phase effect dispersion in a form of dispersion tensor the convective velocity in the resultant equation is the first order lagrangian residual current the sum of the eulerian residual current and the stokes drift the remaining dispersion terms are important only in higher order solutions they are due to shear effect dispersion and turbulent mixing there exists a dispersion boundary layer adjacent to shoreline boundaries an order of magnitude estimate of the properties in the dispersion boundary layer is given the present treatment of intertidal transport processes is illustrated by an analytical solution for an amphidromic system and by a numerical application in south san francisco bay california the present formulation reveals that the mechanism for long term transport of solutes is mainly convection due to the lagrangian residual current in the interior of a tidal estuary this result also points out the weakness in the tidal dispersion formulation and explains the large variability of the observed values for tidal dispersion coefficients further research on properties of the dispersion boundary layer is needed

geochemical indicators in western mediterranean messinian evaporites implications for the salinity crisis abstract the messinian salinity crisis msc led to deposition of one of the youngest saline giant on earth the increasing restriction of the connections between the mediterranean the atlantic ocean and the freshwater paratethyan basins resulted in the deposition of massive amounts of evaporites gypsum anhydrite halite and potash salts in shallow marginal basins as well as in deep mediterranean basins here we show that each gypsum unit in the circum mediterranean marginal basins in sicily and spain is characterized by a narrow range of sulfate isotopic values 34s 23 and 18o 14 in the lower gypsum 34s 23 and 18o 17 in the upper gypsum sulfate isotope compositions found in msc evaporites from a variety of circum mediterranean basins are homogenously high relative to expected late miocene marine evaporites 34s 22 and 18o 12 this points to a stratified mediterranean sea with a high salinity dense and anoxic bottom water mass an intermediate depth gypsum saturated brine flooded marginal basins from which selenite deposits formed during the msc stage 1 primary lower gypsum and msc stage 3 upper gypsum messinian brines were gradually affected by biogenic redox processes and isotopically differentiated from global seawater values the homogeneity of isotopic signatures between distant synchronous gypsum deposits further supports the deep basin deep water model for the mediterranean during the entire msc event

alluvial cutoffs as indicators of former channel conditions although alluvial cutoffs record accurately the geometry bedforms and bed material of the channel when last active few attempts have been made to use cutoffs in studies of channel changes a detailed record of historical channel changes on the lower hunter river in southeastern australia has shown that this channel responds to naturally alternating periods of high and low flood activity called flood and drought dominated regimes respectively sinuosity decreased from 3 84 in 1870 to 2 66 in 1893 and to 1 38 in 1970 through the development of eight cutoffs the channel also aggraded with medium sand burying the former bed material of mixed mud coarse sand and gravel channel straightening was a response to increased flood frequencies during the flood dominated regimes of the late 19th and 20th centuries combined with localized river engineering works and increased sand load detailed stratigraphic studies were carried out on three neck cutoffs and one chute cutoff which were abandoned in 1890 1950 1952 and 1956 a comparison of former and present bed elevations and bed material size showed similar trends to those determined by the historical record confirming the reliability of cutoffs as indicators of former channel conditions the sedimentary infills of the cutoffs are not uniformly fine grained as recorded previously in the literature relatively thin fine grained fills were deposited during the drought dominated regime of the first half of this century but thick coarser grained fills were deposited after 1949 during the flood dominated regime all fills fine upwards cutoff infills provide a record of changing flood activity and sediment loads

age refinement of the messinian salinity crisis onset in the mediterranean we propose a revised age calibration of the messinian salinity crisis onset in the mediterranean at 5 971 ma based on the recognition of an extra gypsum cycle in the transitional interval of the perales section sorbas basin spain and the revision of the magnetostratigraphy of the monticino section vena del gesso basin italy this age re calibration allows to state more accurately that i the interval encompassing the msc onset is continuous thus ruling out any erosional feature or stratigraphic hiatus related to a major sea level fall affecting the mediterranean ii the first gypsum was deposited during the summer insolation peak at 5 969 ma associated with an eccentricity minimum and roughly coincident with glacial stage tg32 iii the msc onset was preconditioned by the tectonically driven reduction of the hydrological exchanges with the atlantic ocean and finally triggered by glacial conditions in the northern hemisphere and by arid conditions in northern africa

terrace aggradation during the 1978 flood on powder river montana usa abstract flood processes no longer actively increase the planform area of terraces instead lateral erosion decreases the area however infrequent extreme floods continue episodic aggradation of terraces surfaces we quantify this type of evolution of terraces by an extreme flood in may 1978 on powder river in southeastern montana within an 89 km study reach of the river we 1 determine a sediment budget for each geomorphic feature 2 interpret the stratigraphy of the newly deposited sediment and 3 discuss the essential role of vegetation in the depositional processes peak flood discharge was about 930 m 3 s 1 which lasted about eight days during this time the flood transported 8 2 million tons of sediment into and 4 5 million tons out of the study reach the masses of sediment transferred between features or eroded from one feature and redeposited on the same feature exceeded the mass transported out of the reach the flood inundated the floodplain and some of the remnants of two terraces along the river lateral erosion decreased the planform area of the lower of the two terraces 2 7 m above the riverbed by 3 2 and that of the higher terrace 3 5 m above the riverbed by 4 1 however overbank aggradation on average raised the lower terrace by 0 16 m and the higher terrace by 0 063 m vegetation controlled the type thickness and stratigraphy of the aggradation on terrace surfaces two characteristic overbank deposits were common coarsening upward sequences and lee dunes grass caused the deposition of the coarsening upward sequences which had 0 02 to 0 07 m of mud at the base and in some cases the deposits coarsened upwards to coarse sand on the top lee dunes composed of fine and very fine sand were deposited in the wake zone downstream from the trees the characteristic morphology of the dunes can be used to estimate some flood variables such as suspended sediment particle size minimum depth and critical shear velocity information about depositional processes during extreme floods is rare and therefore the results from this study aid in interpreting the record of terrace stratigraphy along other rivers

channel adjustments to changing discharges powder river montana sixteen years of annual surveys reveal how powder river responds to varying discharges during 1978 the second largest recorded daily mean discharge occurred cutbank migration bed degradation net bank erosion and overbank deposition all contributed to increase the channel area at 12 cross sections by an average of 62 during the ensuing years the channel area decreased as sediment was stored in low lying benches adjacent to the active bed of the channel the survey data indicate that the balance between bank erosion and deposition varies with discharge in years when the annual maximum daily mean discharge is 3 s a flow of 60 m 3 s has a recurrence interval of 1 1 yr bank erosion and deposition are approximately equal in years when the annual maximum daily mean discharge is between 60 and 150 m 3 s a discharge of 150 m 3 s has a recurrence interval of 2 7 yr bank deposition exceeds bank erosion and the channel contracts often by developing benches in years with higher discharges the channel expands through net bank erosion these results demonstrate that the channel of powder river is influenced by a wide variety of formative discharges powder river9s recent history of expansion and contraction and the development of prominent benches cannot be explained by equilibrium models based on a single channel forming discharge

the messinian of the nijar basin se spain sedimentation depositional environments and paleogeographic evolution abstract the reconstruction of the depositional events related to the messinian salinity crisis msc of the mediterranean is generally hampered by an incomplete stratal record in the circum mediterranean basins the sediments of the northern part of the nijar basin however provide an excellent and continuous record of late messinian sediments because features of severe erosion are lacking especially the successions of the deeper part of the basin had sufficient accommodation space to warrant ongoing deposition and may thus serve as a testing ground for existing hypotheses regarding the msc conformable contacts with the overlying pliocene and good correlation possibilities with the adjacent astronomically dated messinian of the sorbas basin provide the necessary age constraints the main body of evaporites in the nijar basin yesares formation has been affected by local dissolution and erosion prior to deposition of the latest messinian lago mare facies pelitic float breccias show textures indicating flowage and or mass transport and include slumped and slided stratal packets due to foundering of the mixed evaporitic clastic margin increased runoff of meteoric waters probably played an important role as these packet slides are perfectly sealed by the hyposaline lago mare strata field observations show that marginal sediments commonly classified as the terminal carbonate complex tcc are a lateral equivalent of the basinal yesares evaporites the latest messinian deposits feos formation are characterized by a sedimentary cyclicity related to fluctuating base levels consisting of chalky marly laminitic strata alternating with continental coarser clastic intervals despite considerable w e facies changes and indications for discrete tectonic events a persistent sequential pattern of eight lago mare cycles is present which are interpreted as precession controlled variations in regional climate instead of one major desiccation event in the latest messinian the repeatedly fluctuating water levels of the lago mare episode may have been the cause of the widespread vigorous erosion and canyon cutting in the lower evaporites abrupt non erosional contacts with the normal marine pliocene take place above the continental interval of the last lago mare cycle indicating that flooding took place during a period of lowered water levels the paleogeographic configuration of the nijar sorbas and vera basins has changed considerably during the messinian separation of the formerly interconnected basins is thought to have started in the late yesares times by tectonic uplift of the basement complexes in the latest messinian of the nijar basin two different coarse clastic supply areas can be distinguished which point to the partial emergence of the sierra cabrera and the cabo de gata block and activity of the sierra alhamilla and carboneras faults concerning the overall regional tectonic activity tectonics were probably also instrumental for the restoration of the atlantic gateway in the basal pliocene

accuracy assessment of georectified aerial photographs implications for measuring lateral channel movement in a gis aerial photographs are commonly used to measure planform river channel change we investigated the sources and implications of georectification error in the measurement of lateral channel movement by testing how the number 6 30 and type human versus natural landscape features of ground control points gcps and the order of the transformation polynomial first second and third order affected the spatial accuracy of a typical georectified aerial photograph error was assessed using the root mean square error rmse of the gcps as well as error in 31 independent test points the rmse and the mean and median values of test point errors were relatively insensitive to the number of gcps above eight but the upper range of test point errors showed marked improvement i e the number of extreme errors was reduced as more gcps were used for georectification using more gcps thus improved overall georectification accuracy but this improvement was not indicated by the rmse suggesting that independent test points located in key areas of interest should be used in addition to rsme to evaluate georectification error the order of the transformation polynomial also influenced test point accuracy the second order polynomial function yielded the best result for the terrain of the study area gcp type exerted a less consistent influence on test point accuracy suggesting that although hard edged points e g roof corners are favored as gcps some soft edged points e g trees may be used without adding significant error based upon these results we believe that aerial photos of a floodplain landscape similar to that of our study can be consistently georectified to an accuracy of approximately f5 m with 10 chance of greater error the implications of georectification error for measuring lateral channel movement are demonstrated with a multiple buffer analysis which documents the inverse relationship between the size of the buffers applied to two channel centerlines and the magnitude of change detected between them this study demonstrates the importance of using an independent test point analysis in addition to the rsme to evaluate and treat locational error in channel change studies d 2005 published by elsevier b v

fluvial process and the establishment of bottomland trees the effects of river regulation on bottomland tree communities in western north america have generated substantial concern because of the important habitat and aesthetic values of these communities consideration of such effects in water management decisions has been hampered by the apparent variability of responses of bottomland tree communities to flow alteration when the relation between streamflow and tree establishment is placed in a geomorphic context however much of that variability is explained and prediction of changes in the tree community is improved the relation between streamflow and establishment of bottomland trees is conditioned by the dominant fluvial process or processes acting along a stream for successful establishment cottonwoods poplars and willows require bare moist surfaces protected from disturbance channel narrowing channel meandering and flood deposition promote different spatial and temporal patterns of establishment during channel narrowing the site requirements are met on portions of the bed abandoned by the stream and establishment is associated with a period of low flow lasting one to several years during channel meandering the requirements are met on point bars following moderate or higher peak flows following flood deposition the requirements are met on flood deposits high above the channel bed flood deposition can occur along most streams but where a channel is constrained by a narrow valley this process may be the only mechanism that can produce a bare moist surface high enough to be safe from future disturbance because of differences in local bedrock tributary influence or geologic history two nearby reaches of the same stream may be dominated by different fluvial processes and have different spatial and temporal patterns of trees we illustrate this phenomenon with examples from forests of plains cottonwood populus deltoides ssp monilifera along meandering and constrained reaches of the missouri river in montana

tectonic inversion of an asymmetric graben insights from a combined field and gravity survey in the sorbas basin the formation of sedimentary basins in the alboran domain is associated with the exhumation of metamorphic core complexes over a ca 15 ma period through a transition from regional late orogenic extension to compression an integrated study coupling field analysis and gravity data acquisition was performed in the sorbas basin in the southeastern betic cordillera detailed field observations revealed for the first time that extensional tectonics occurred before shortening in this basin two extensional events were recorded with nw se to n s and ne sw kinematics respectively the first of which being likely responsible for the basin initiation tectonic inversion of the basin then occurred around 8 ma in an overall ca n s shortening context 2d gravity sections reveal that the basin acted as an active depocenter as the basin floor locally exceeding 2 km depth is characterized by a marked asymmetric architecture based on this integrated study we explore a new evolutionary scenario which can be used as a basis for interpretations of the neogene tectonic history of the southeastern betics

apparent increasing rates of stream incision in the eastern united states during the late cenozoic stream incision rates were obtained from 16 studies of terraces or stream associated cave levels in the eastern united states a log log regression of age against height above modern river level arl shows that age increases approximately as the square of height arl this relation may indicate an increasing rate of stream incision through time alternatively the relation may simply reflect an inherent effect of measured time interval on process rate as described by gardner et al who found that data from hundreds of studies showed a tendency for geologic process rates to decrease for increasing measurement intervals a regression equation for landscape denudation rates showed that the thickness removed increased as the 0 82 power of the time interval over which the denudation was measured gardner et al suggested that this bias could be removed by the use of statistically derived scaling functions however a similar regression equation for the data in this study shows a slope of 0 38 representing a much more rapid decrease in rate with increasing measurement interval than found by gardner et al even after applying the scaling function calculated by gardner et al my data show a 19 fold decrease in incision rate for a 103 increase in the measured time interval this result suggests that the observed decrease in stream incision rates with greater time spans may be at least partly real

climatic controls on the snowmelt hydrology of the northern rocky mountains abstract the northern rocky mountains nrms are a critical headwaters region with the majority of water resources originating from mountain snowpack observations showing declines in western u s snowpack have implications for water resources and biophysical processes in high mountain environments this study investigates oceanic and atmospheric controls underlying changes in timing variability and trends documented across the entire hydroclimatic monitoring system within critical nrm watersheds analyses were conducted using records from 25 snow telemetry snotel stations 148 1 april snow course records stream gauge records from 14 relatively unimpaired rivers and 37 valley meteorological stations over the past four decades midelevation snotel records show a tendency toward decreased snowpack with peak snow water equivalent swe arriving and melting out earlier temperature records show significant seasonal and annual decreases in the number of frost days days 0 c and changes in spring minim

geologic evolution of the betic cordilleras in the western mediterranean miocene to the present abstract the betic cordilleras were formed during the eo meso and neo alpine evolution of the western mediterranean area during the neo alpine stage the northward subduction of the african plate took place and the algerian provencal basin opened with the creation of oceanic floor associated space problems produced the expulsion and extensive stretching of the internal zones to the west which in turn disrupted and deformed the external zones of the betic and rif cordilleras these occurrences essentially took place in the burdigalian and continued with diminished intensity into the middle miocene following the suturing of the transcurrent contact between the internal and external zones important n60 90 e and nw se faults occurred the betic cordilleras are characterized as having been deformed by regional horizontal shortening compression oriented wnw ese or nw se which gradually rotated to the nnw sse in the late miocene when its most important intramontane neogene basins were formed the alboran basin with a thinned continental crust was formed as a western prolongation of the opening of the algerian provencal basin with its basic features already apparent in the burdigalian the volcanism present in the southeast of the betic cordilleras and in northeast morocco crossing the alboran basin is mainly late miocene in age it is linked to fracturing and exhibits chemistry related to the different thickness of the crust

coupled measurements of δ18o and δd of hydration water and salinity of fluid inclusions in gypsum from the messinian yesares member sorbas basin se spain we studied one cycle cycle 6 of gypsum marl deposition from the messinian yesares member in sorbas basin spain the objective was to reconstruct the changing environment of deposition and its relation to astronomically forced climate change the 18o and d of gypsum hydration water caso4 2h2o and salinity of fluid inclusions were measured in the same samples to test if they record the composition of the mother fluid from which gypsum was precipitated water isotopes are highly correlated with fluid inclusion salinity suggesting the hydration water has not exchanged after formation the relatively low water isotope values and fluid inclusion salinities indicate a significant influence of meteoric water whereas 34s 18oso4 and 87sr 86sr support a dominant marine origin for the gypsum deposits the discrepancy between water and elemental isotope signatures can be reconciled if meteoric water dissolved previously deposited marine sulfates supplying calcium and sulfate ions to the basin which maintained gypsum saturation this recycling process accounts for the marine 34s 18oso4 and 87sr 86sr signatures whereas the low 18o and d values of gypsum hydration water and fluid inclusion salinities reflect the influence of freshwater the cyclic deposition of gypsum and marl in the yesares member has previously been interpreted to reflect changing climate related to earth s precession cycle we demonstrate that the 18o d and salinity of the parent brine increased from low values at the base of the cycle to a maximum in the massive gypsum palisade and decreased again to lower values in the supercones at the top of the cycle this pattern together with changes in mineralogy calcite dolomite gypsum is consistent with a precession driven change in climate with wettest conditions summer insolation maxima associated with the base of the calcium carbonate marls and driest conditions summer insolation minima during formation of the gypsum palisade

the measurement of river bank erosion and lateral channel change a review a detailed review and chronological survey is presented of the various techniques which have been used for the measurement of river bank erosion and channel change the techniques are classified according to the time scales involved long intermediate and short and each is discussed with respect to accuracy and repeatability the methods covered include sedimentological evidence botanical evidence historical sources planimetric resurvey repeated cross profiling erosion pins and terrestrial photogrammetry prospects for future developments are also discussed

microbial deposits in upper miocene carbonates mallorca spain the santanyi limestone a 30 35 m thick upper miocene limestone succession cropping out in mallorca contains abundant microbialite deposits the shape microstructure and texture of which was controlled by environmental factors depth energy and salinity three main types of microbialites are distinguished 1 domed dnos and stratiform mostly undulate unos non oolitic stromatolites 2 undulate oolitic laminites uol and 3 domed oolitic thrombolites dots based on lithofacies associations and occurrence of microbialite types the santanyi limestone succession is subdivided into five stratigraphic units i to v separated by sharp surfaces within units ii iii and v the vertical evolution of microbialites was induced by changes in accommodation space depth 1 intertidal very shallow subtidal conditions at the base were induced by flooding over a wide area 2 continued sea level rise caused submergence to subtidal conditions and 3 a significant bathymetric decrease created the sharp surface bounding these units in units ii and iii nos accumulated in variable energy and depth conditions as buildups with thick somewhat discontinuous and mostly non isopachous lamination surrounded by oolitic grainstones with wave and current structures and oolitic intraclasts in contrast thin and generally regular and smooth lamination of nos in unit v suggests along with the absence of oolite grainstones and macrobiota calm and restricted maybe more saline conditions uol consisting of oolitic layers separated by thin micritic laminae developed adjacent to nos in units ii and iii and to dot at the lower part of unit iii in shallow water and low energy conditions both ooids and micrite laminae have evidence for biogenesis micritized ooids containing microbial remains are common micritic laminae in uol and the dark micritic laminae in nos are thought to represent bacterially enhanced calcite precipitation and lithification during periods of low sedimentation oolitic thrombolites containing macrobiota are only present in unit iii they represent deeper and open marine conditions affected by high energy events in which microbially mediated precipitation favoured microbialite accretion and lithification

marine carbonate factories a global model of carbonate platform distribution platform carbonates are a major component of the earth system but their spatial distribution through geological times is difficult to reconstruct due to the incompleteness of geological records sampling heterogeneity and their intrinsic complexity beyond this complexity carbonates are not randomly distributed in the world oceans neither in the modern nor in the past and thus global trends exist in the present review we focus on the understanding of the spatial distribution of carbonate production at a global scale we use a deterministic approach which focuses on discriminating components stratigraphic architectures and environmental features to relate shallow water carbonate production to oceanographic parameters the work is based on extensive literature reviews on carbonate platforms ecological niche modelling coupled with deep time general circulation models is used to calibrate a predictive tool of carbonate factory distribution a carbonate factory function is set up that is based on sea surface oceanographic parameters temperature salinity and primary productivity the model was tested using remote sensing and in situ oceanographic data of modern times while outputs of paleoceanographic models are utilized for lower aptian cretaceous modelling the approach allows determining four neritic carbonate factories that are called the marine biochemical photozoan photo c and heterozoan factories the model finely simulates the global distribution of lower aptian and modern carbonate platforms carbonate factories appear to thrive for specific ranges along the environmental gradient of carbonate saturation this conceptual scheme appears to be able to provide a simple universal model of paleoclimatic zones of shallow water marine carbonates

harmonic analysis of tides and tidal currents in south san francisco bay california abstract water level observations from tide stations and current observations from current meter moorings in south san francisco bay south bay california have been harmonically analysed at each tide station 13 harmonic constituents have been computed by a least squares regression without inference tides in south bay are typically mixed there is a phase lag of approximately 1 h and an amplification of 1 5 from north to south for a mean semi diurnal tide because most of the current meter records are between 14 and 29 days only the five most important harmonics have been solved for east west and north south velocity components the eccentricity of tidal current ellipse is generally very small which indicates that the tidal current in south bay is strongly bidirectional the analyses further show that the principal direction and the magnitude of tidal current are well correlated with the basin bathymetry patterns of eulerian residual circulation deduced from the current meter data show an anticlockwise gyre to the west and a clockwise gyre to the east of the main channel in the summer months due to the prevailing westerly wind opposite trends have been observed during winter when the wind was variable

flood plain and channel dynamics of the quinault and queets rivers washington usa abstract comparison of historic channel migration rates modern planform conditions and overall sediment wood and flow conditions and interactions for the quinault river and queets river in the western olympic peninsula washington reveals decadal to century scale interactions between gravel bed channels and forested flood plains in temperate maritime environments the downstream alluvial portions of these two rivers can be divided into three reaches of different slope flow sediment and wood regimes i the upper quinault river is aggrading behind lake quinault a natural lake that traps most sediment and wood transported from the olympic mountain headwaters ii the lower quinault river downstream of lake quinault transports only sediment and wood derived from reworking of flood plain deposits and contributed from valley margins iii the queets river has unimpeded movement of sediment and water from the mountainous headwaters to the pacific ocean measurements of channel planform characteristics and historic migration rates and patterns show that these three reaches have correspondingly distinct channel and flood plain morphologies and dynamics the aggrading and sediment rich upper quinault river has the widest flood plain widest active channel greatest number of low flow channels and flanking gravel bars and an average channel migration rate of 12 7 3 3 m year between 1900 and 1994 the comparatively sediment poor lower quinault river has the narrowest flood plain narrowest active channel and lowest channel migration rate 4 0 1 2 m year and most flow is through a single channel with few adjacent gravel bars the queets river has attributes intermediate between the lower and upper quinault rivers including an average channel migration rate of 7 5 2 9 m year flood plain turnover rates are similar for all three reaches with channels eroding the flood plain at the rate of about 0 2 of the flood plain area per year and with corresponding flood plain half lives of 300 to 500 years observations from this study and previous studies on the queets river show that channel and flood plain dynamics and morphology are affected by interactions between flow sediment and standing and entrained wood some of which likely involve time frames similar to 200 500 year flood plain half lives on the upper quinault river and queets river log jams promote bar growth and consequent channel shifting short distance avulsions and meander cutoffs resulting in mobile and wide active channels on the lower quinault river large portions of the channel are stable and flow within vegetated flood plains however locally channel spanning log jams have caused channel avulsions within reaches that have been subsequently mobile for several decades in all three reaches log jams appear to be areas of conifer germination and growth that may later further influence channel and flood plain conditions on long time scales by forming flood plain areas resistant to channel migration and by providing key members of future log jams appreciation of these processes and dynamics and associated temporal and spatial scales is necessary to formulate effective long term approaches to managing fluvial ecosystems in forested environments

did late miocene messinian gypsum precipitate from evaporated marine brines insights from the piedmont basin italy during the first stage of the late miocene messinian salinity crisis 5 97 5 60 ma deposition of sulfates the primary lower gypsum occurred in shallow silled peripheral subbasins of the mediterranean undergoing restricted water exchange with the atlantic ocean fluid inclusions in messinian selenite crystals from the piedmont basin northwest italy have surprisingly low salinities average of 1 6 wt nacl equivalent suggesting that parent waters were depleted in na and cl compared to modern seawater modern gypsum from a mediterranean salt work in contrast contains fluid inclusions with elevated salinities that match the normal evaporation trend expected for seawater the salinity data indicate that the messinian sulfate deposits from the piedmont basin formed from hybrid parent waters seawater mixed with ca 2 and so 4 2 enriched freshwaters that dissolved coeval marginal marine gypsum such mixed parent waters and complex recycling processes should be taken into account when explaining the genesis of other messinian gypsum deposits across the mediterranean basin

geomorphic and tectonic process rates effects of measured time interval analysis of the original numerical components of diverse geomorphic and tectonic process rates indicates that process rate is not independent of measured time interval this implies that direct comparison of geologic process rates measured over variable time intervals may not be valid and that conclusions based on those comparisons regarding changes in rates through geologic time may be misleading in some cases calculation of statistically derived scaling functions is one approach that can be used to account for this measurement interval bias and to improve comparisons of geologic process rate data when this approach is used a 10 4 or 10 5 yr variation in the measured time interval accounts for approximately one order of magnitude change in the measured process rate the magnitude of the correction can substantially affect conclusions of studies that compare uncorrected process rates calculated from variable time intervals

structure and evolution of a messinian mixed carbonate siliciclastic platform the role of evaporites sorbas basin south east spain the sorbas member is a late messinian complex sedimentary system that formed immediately following deposition of the messinian evaporites in the sorbas basin south east spain this work describes the sequence architecture and facies organization of a continuous kilometre long alluvial fan to open platform transect near the village of cariatiz in the north east of the basin the post evaporitic cariatiz platform was a mixed carbonate siliciclastic system composed of four intermediate frequency fifth order depositional sequences depositional sequences 1 to 4 arranged in an overall prograding trend the intense fracturing and brecciation of these deposits is attributed to the deformation and dissolution of an evaporite body measuring several tens of metres in thickness the four sequences display significant spatial temporal variability in both architecture and facies distribution with two main phases i depositional sequences 1 and 2 are ooid and oobioclastic dominated and show normal marine faunas and ii depositional sequences 3 and 4 show a higher siliciclastic contribution and are microbialite dominated these important changes are interpreted as modifications of the primary controlling factors following an initial 70 m drowning possibly linked to increased oceanic input depositional sequences 1 to 3 were controlled mainly by eustatic variations and inherited topography their progradation destabilized the evaporite body near the end of the depositional sequence 2 period during the second phase depositional sequences 3 and 4 recorded a progressive restriction of the sorbas basin related to a 30 to 40 m fall in water level that was driven mainly by regional factors these regional factors were dissolution and gravity induced deformation of the evaporites and correlative evaporative fluid circulation associated with the contrasted arid humid regional climate that respectively controlled sequence geometry and fluctuating water salinity which caused a microbialite bloom