spatial organization in the step pool structure of a steep mountain stream vogelbach switzerland 1 spatial organization in the step pool structure of a 1 58 km long section of the vogelbach a steep mountain stream average channel bed slope 0 17 m m in the alpthal basin switzerland is analyzed to evaluate the extent of randomness in the occurrence of steps and to isolate the potential hydraulic and topographic controls on step placement statistics of the observed step sequence are compared with those of random sequences generated by permutation from the observed step height distribution hydraulic and topographic controls on step placement are analyzed from step length and steepness distributions and relations between mean step properties and step height and channel gradient for both observed and random sequences results show that 1 observed step length distributions are statistically significantly different from randomly generated sequences 2 step steepness is significantly different in observed data because of a positive correlation between mean step length and height and it remains fairly constant for all step sizes 3 spatial organization in steps does not extend far beyond the nearest step and 4 the influence of channel gradient on step properties is insignificant and highly variable indicating that hydraulic rather than topographic controls are dominant for step placement in this stream although the vogelbach is a steep stream on the boundary between a cascading and step pool morphology where we would expect randomness to dominate spatial organization was nevertheless detected in many important aspects of the step pool geometry

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

sea level controls sedimentation and environments in coastal caves and sinkholes abstract quaternary climate and sea level research in coastal karst basins caves cenotes sinkholes blueholes etc generally focuses on analyzing isotopes in speleothems or associating cave elevations prior sea level highstands the sediments in coastal karst basins represent an overlooked source of climate and sea level information in the coastal zone but to accurately interpret these sediments first requires an understanding of the forcing mechanisms that emplace them in this study we hypothesize that coastal karst basins transition through vadose littoral anchialine and finally into submarine environments during sea level rise because groundwater and sea level oscillate in near synchrony in the coastal zone causing each environment to deposit a unique sedimentary facies to test this hypothesis the stratigraphy in twelve sediment cores from a bermudian underwater cave green bay cave was investigated and temporally constrained with twenty radiocarbon dates the results indicate that we recovered the first succession spanning the entire holocene from an underwater cave 13 ka to present the sediments were characterized with x radiography fossil remains bulk organic matter organic geochemistry 13corg c n and grain size analysis four distinct facies represent the four depositional environments i vadose facies 7 7 ka calcite rafts lithofacies ii littoral facies 7 7 to 7 3 ka calcite rafts and mud lithofacies iii anchialine facies 7 3 to 1 6 ka slackwater and diamict lithofacies and iv submarine facies

assessing δ13c and c n ratios from organic material in archived cores as holocene sea level and palaeoenvironmental indicators in the humber estuary uk organic 13c and c n analyses of estuarine deposits provide proxies for changes in the source of organic matter which can be driven by fluctuations in relative sea level river discharge and catchment disturbance here we present the results of a comprehensive vegetation and sediment 13c and c n survey of welwich marsh outer humber estuary uk together with high resolution 13c and c n analyses of holocene cores collected nine years previously from the humber estuary and the lincolnshire marshes eastern england uk the contemporary intertidal 13c and c n dataset shows a gradual increase in surface sediment 13c with decreasing marsh height and suggests that 13c is controlled by the degree of tidal inundation and thus reflects organic matter source however sediment c n ratios are less sensitive to tidal changes and the recent introduction of c4 salt marsh species complicates the contemporary analogue the holocene 13c and c n records are in general agreement with existing microfossil data and provide additional palaeoenvironmental information this includes support for an estuary wide expansion of marine conditions from c 3 3 ka cal yr bp followed by a contraction of marine conditions after c 2 7 ka cal yr bp and evidence for an increase in delivery of terrigenous organic matter to the inner estuary in the late holocene bulk organic 13c and c n analysis is shown to be a reliable and independent indicator of coastal environmental change and is therefore a complementary technique to the more commonly used microfossil approach however this study also shows that in some circumstances the technique may be compromised when applied to sediments from cores that have been stored for a period of time

interference processes on scouring at bed sills the local scouring downstream of bed sills forming a sequence for bed stabilization in steep channels has been investigated in a laboratory flume the initial bed slopes ranged from 0 078 to 0 148 the bed alluvium was characterised by a non uniform grain size distribution the results show that when the ratio between the critical water depth hc and the sill spacing l rises above a characteristic value the scouring dynamics become heavily affected by the presence of the downstream sill associated with the onset of a form of interference which renders the scouring process less effective the difference with an undisturbed case is demonstrated self affinity of scour holes is confirmed and the scour length appears to be the reference parameter from which the scour depth might be evaluated copyright 2003 john wiley sons ltd

effect of grade control structures at various stages of their destruction on bed sediments and local channel parameters abstract grade control structures gcss represent the typical management of torrential streams preventing massive bed erosion and bedload transport the original and present geometric and sedimentary parameters of 18 gcss at various stages of their destruction since the 1970s were evaluated to determine the relationship between the former and present day components of the managed mohelnice river the western carpathians czech republic the latest changes in the gcs geometry related scour holes and bed surface grain size of sedimentary wedges were caused by the 2010 flood event of 20 50 r i discharge no relationship exists between the bed surface grain sizes and the present water drop or the present equilibrium channel slope of the sedimentary wedge a significant downstream coarsening of the largest grain size percentile represented by d 95 is detected through the sequence of gcss also statistically insignificant trends in downstream coarsening were observed for d 16 d 50 and d 84 grain sizes however the investigated sequence is still passable for grain diameters up to 200 mm during high magnitude floods similar to the 2010 event as documented by the development of a confluent gravel bar downstream of the sequence bedload transport simulations provide the highest bedload transport rates for the initial stage of the uppermost studied channel reach without the presence of gcss 30 000 kg min 1 for q 50 grade control structures reconstruction in the 1970s significantly decreased transport rates 2000 kg min 1 for q 50 owing to the erosion of gcs crests and an increase in related equilibrium channel slope damage on gcss can lead to an increase in bedload transport intensity 13 000 kg min 1 for q 50 significant linear relationships exist among the present parameters of the scour holes length of scour hole maximum scour depth and horizontal distance between the point of maximum depth and the gcs crest a statistical significant power relationship exists between the parameters of maximum scour hole depth and the present drop height showing adjustments of maximum scours to the present stage of gcss and the last flood event

the kap gustav holm tertiary plutonic centre east greenland the plutonic centre is exposed on the narrow headland of kap gustav holm in east greenland it was emplaced into the hinge zone of a major crustal flexure that developed during initial rifting between greenland and northwest europe the earliest intrusion is a funnel shaped tholeiitic gabbro that was emplaced into the developing flexure probably about 55 ma ago the intrusion comprises a basal contact zone of gabbro 100m thick showing syn plutonic deformation and recrystallization a lower zone of massive olivine gabbro 250 1500 m thick and an upper zone of layered gabbro with a minimum thickness of 500 700 m all are cut by sheets of gabbro pegmatite abrupt reversals in cryptic and phase layering suggest that the gabbro intrusion is the result of several injections of magma the gabbro intrusion was tilted steeply seawards before emplacement of plutons and sheets of monzonite syenite and granite about 50 ma ago the main monzonite body forms a vertical cylinder 2 5 km in diameter with saucer shaped mineral graded layering and abundant volcanic inclusions regular stratigraphic variation in the composition of plagioclase and augite with structural height is interrupted by an abrupt reversal suggesting emplacement of a new pulse of magma syenite forms ring dykes and partial ring dykes of two distinct compositions an older subalkaline syenite related to the monzonite and gabbro and a younger mildly peralkaline syenite granite forms a small composite pluton abundant syn plutonic bodies of microdioite are associated with monzonite syenite and granite intrusions

hydraulics morphology and energy dissipation in an alpine step pool channel 1 to investigate the relationship between hydraulics and channel morphology in step pool channels we combined three dimensional velocity measurements with an acoustic doppler velocimeter and topographic surveys in a steep step pool channel the rio cordon italy measurements were organized around step pool and tread units and occurred within a range of 36 57 of bankfull discharges as flow moved from steps to their downstream pools in our study reach an average of approximately two thirds of the total energy was dissipated as measured by relative head loss through step pool sequences much of this head loss was achieved by elevation potential energy loss rather than velocity reductions although an overall expected pattern of flow acceleration toward step crests and deceleration in pools was present pool velocities were high especially where upstream step crests were irregular and where residual pool depths were low many steps were porous or leaky with irregular cross channel bed and water surface topography producing high velocity jets and less flow resistance than channel spanning dammed steps longitudinal variations in hydraulics are thus often overshadowed by lateral variations arising from morphologic complexities velocity and turbulence characteristics in the rio cordon show marked differences from data we have collected in a more stable and wood rich channel in the colorado rockies in which ponded steps are more prevalent and pools are slower and more turbulent comparison of these channels illustrates that step pool structure and hydraulics are strongly influenced by flow regime sediment supply lithology time since the last step forming flood and availability of in stream wood

experimental study on the stability and failure of individual step pool abstract step pools are one of the most common bedforms in mountain streams the stability and failure of which play a significant role for riverbed stability and fluvial processes given this importance flume experiments were performed with a manually constructed step pool model the experiments were carried out with a constant flow rate to study features of step pool stability as well as failure mechanisms the results demonstrate that motion of the keystone grain ks caused 90 of the total failure events the pool reached its maximum depth and either exhibited relative stability for a period before step failure which was called the stable phase or the pool collapsed before its full development the critical scour depth for the pool increased linearly with discharge until the trend was interrupted by step failure variability of the stable phase duration ranged by one order of magnitude whereas variability of pool scour depth was constrained within 50 step adjustment was detected in almost all of the runs with step pool failure and was one or two orders smaller than the diameter of the step stones two discharge regimes for step pool failure were revealed one regime captures threshold conditions and frames possible step pool failure whereas the second regime captures step pool failure conditions and is the discharge of an exceptional event in the transitional stage between the two discharge regimes pool and step adjustment magnitude displayed relatively large variabilities which resulted in feedbacks that extended the duration of step pool stability step adjustment which was a type of structural deformation increased significantly before step failure as a result we consider step deformation as the direct explanation to step pool failure rather than pool scour which displayed relative stability during step deformations in our experiments

effects of check dams on bed load transport and steep slope stream morphodynamics abstract check dams are transversal structures built across morphologically active streams in mountainous regions these structures have been used widely in torrent hazard mitigation for over 150 years thousands of them are regularly maintained by stream managers and torrent control services the stabilization role of these structures is well known i e they durably constrain the stream bed through the creation of vertical and planar fixed points what is not yet clear is to what extent check dams influence bed load transport how do peak solid discharge or flood transported volume change when check dams are added to a reach to address these questions long lasting small scale experiments were conducted in a 4 8 m long flume with either one three or no structures the results show that the addition of structures creates independent compartments in the bed level which have a strong influence on bed surface armouring and stream morphodynamics the consequence is that instantaneous transport intensities are unchanged but peak solid discharge occur more often and for shorter duration this results in the same total transported volume over the long term but reduced volume for a single transport event it reaffirms the observation of pioneering authors of the mid 19th and early 20th century who conceptualized the possible sediment transport regulation function of check dams in addition to stabilizing the stream bed check dams influence bed load transport through a buffering effect releasing frequently and in small doses what in their absence would be transported abruptly en masse during rare extreme events

late neogene and quaternary evolution of the northern albemarle embayment mid atlantic continental margin usa seismic surveys in the eastern albemarle sound adjacent tributaries and the inner continental shelf define the regional geologic framework and provide insight into the sedimentary evolution of the northern north carolina coastal system lithoand chronostratigraphic data are derived from eight drill sites on the outer banks barrier islands and the mobil 1 well in eastern albemarle sound within the study area parallel bedded gently dipping miocene beds occur at 95 to n160 m below sea level m bsl and are overlain by a southward thickening pliocene unit characterized by steeply inclined southward prograding beds the lower pliocene unit consists of three seismic sequences the 55 60 m thick quaternary section unconformably overlies the pliocene unit and consists of 18 seismic sequences exhibiting numerous incised channel fill facies shallow stratigraphy b40 m bsl is dominated by complex fill patterns within the incised paleo roanoke river valley radiocarbon and amino acid racemization aar ages indicate that the valley fill is latest pleistocene to holocene in age at least six distinct valley fill units are identified in the seismic data cores in the valley fill contain a 3 6 m thick basal fluvial channel deposit that is overlain by a 15 m thick unit of interlaminated muds and sands of brackish water origin that exhibit increasing marine influence upwards organic materials within the interlaminated deposits have ages of 13 11 cal ka the interlaminated deposits within the valley are overlain by several units that comprise shallow marine sediments bay mouth and shoreface environments that consist of silty fine to medium grained sands containing open neritic foraminifera suggesting that this area lacked a fronting barrier island system and was an open embayment from 10 ka to 4 5 ka seismic data show that initial infilling of the paleo roanoke river valley occurred from the north and west during the late pleistocene and early holocene later infilling

organic carbon isotope systematics of coastal marshes abstract measurements of nitrogen organic carbon and 13c are presented forspartina dominated marsh sediments from a mineral marsh in sw netherlands and from a peaty marsh in massachusetts u s a 13c of organic carbon in the peaty marsh sediments is similar to that ofspartinamaterial whereas that in mineral marshes is depleted by 9 12 it is argued that this depletion in 13c of organic matter in marsh sediments is due to trapping of allochthonous organic matter which is depleted in13c the isotopic composition and concentration of organic carbon are used in a simple mass balance to constrain the amount of plant material accumulating in marsh sediments i e in terms of the so called net ecosystem production net ecosystem production 2 100 g c m 2year 1 is a small fraction 1 5 of plant production 2000 g c m 2year 1 this small amount of plant material being preserved is nevertheless sufficient to support marsh accretion rates similar to the rate of sea level rise

sediments deposited by the 2004 indian ocean tsunami along the malaysia thailand peninsula stratigraphy grain size distribution and foraminiferal assemblages of pre tsunami and tsunami sediment from the indian ocean tsunami at five sites along the malaysia thailand peninsula were analyzed to gain information on tsunami sediment source and deposition style between three and five stratigraphic units were identified at each site and contained between one and three fining upward sequences reflecting waning flow or pre backwash deposition coarser sand layers reflecting uprush high energy flow separated the fining upward sequences with the exception of one site sungai burong which contained a coarsening upward sequence all contacts between the pre tsunami and tsunami sediment were sharp or erosional medium and coarse sand dominated all of the tsunami sediment deposits and often contained shell fragments foraminiferal assemblages were able to differentiate pre tsunami sediment from tsunami sediment where no lithological or grain size distribution change was evident between two and four foraminiferal zones were identified at each of the five sites and provided estimates of sediment source and wave characteristics

how stable is the mississippi delta large deltas are commonly believed to exhibit rapid rates of tectonic subsidence largely due to sediment loading of the lithosphere as a result deltaic plains are prone to accelerated relative sea level rise coastal erosion and wetland loss hurricane katrina s devastation testifies to the severe threat that these processes pose to the mississippi delta but the relative role of tectonics versus other mechanisms causing land subsidence remains elusive relative sea level records derived from basal peat have the potential to quantify differential crustal movements over holocene time scales with exceptionally high accuracy and precision here we present new sea level index points from two study areas in the southwestern mississippi delta that essentially coincide with a recently published detailed relative sea level record from the eastern part of the delta our results show that differential vertical movements among the three study areas have been only 0 1 mm yr 1 w e compare our evidence with a recent sea level compilation from the caribbean to a large extent based on data from areas that are tectonically stable our sea level index points nearly coincide with the caribbean data showing surprising tectonic stability for considerable sections of the mississippi delta however the well documented high subsidence rates in and near the birdfoot of the mississippi delta indicate that different conditions prevail there the rapid wetland loss in coastal louisiana is likely due to a considerable extent to the compaction of holocene strata

principles of engineering geomorphology for managing channel erosion and bedload transport examples from french rivers abstract french rivers have been transformed by centuries of development to satisfy various social demands such as navigation hydro electric power production flood control or checking erosion these modifications have led to impacts that are detrimental to ecology to resources and to human interests in recent years increased public and management awareness of these problems has given way to new conceptions and objectives in the field of river engineering among which the goal of establishing sustainable long term management strategies is of the highest importance because many of these problems are directly or indirectly related to changes in the geomorphological functioning of fluvial systems there is a need to integrate a geomorphological approach into river engineering practices the principles of engineering geomorphology are developed here and are illustrated by examples taken from rivers that drain the french alps and their piedmont

adjustments in channel form sediment calibre and vegetation around check dams in the headwater reaches of mountain torrents calabria italy the structure and dynamics of vegetation in valley bottoms are both strongly associated with fluvial processes and landform dynamics all of these associations are disrupted by the installation of engineering control works we use survey and analysis methods developed previously to investigate the impact of the installation of check dams within the confined headwaters of steep seasonally flowing streams fiumaras in calabria southern italy on active channel form sediment calibre and the richness cover and development of riparian vegetation based on detailed field measurements along transects across the active channel estimates of indices of vegetation extent gcc development wch and their cross sectional variability coefficients of variation of both indices at each survey site cvgcc cvwch the number of species present ns channel shape w d the width depth ratio cross sectional area csa downstream gradient slope surface bed sediment calibre d50 and subsurface fine sediment content percentage less than 250 m by weight were obtained for 60 transects located immediately upstream u downstream d and at intermediate sites i around 20 check dams located in four different headwater catchments analysis of this data set suggests that statistically significant changes in channel form and sediment calibre upstream of check dams are associated with more consistent vegetation development across the active channel including an increase in species richness relative to other transects but notable increases in vegetation cover and development only arise where the physical characteristics of the channel are notably different from intermediate and downstream channels because of the naturally steep profile of the study torrents intermediate sections between check dams tend to be more similar in form to channels located immediately downstream of check dams than those located upstream leading to similar structural properties in the riparian vegetation the intermediate transects support considerably more species than downstream reaches but the conditions upstream of the check dams appear to be so favourable for riparian vegetation development that species richness exceeds that found in intermediate reaches despite the confined headwater locations these contrasts in form sediment and vegetation development around check dams are strong and consistent across the study catchments over riding more subtle contrasts in species richness and sediment calibre between catchments copyright 2009 john wiley sons ltd

a review of coastal palaeoclimate and relative sea level reconstructions using δ13c and c n ratios in organic material holocene reconstructions of relative sea level rsl and environmental change in the coastal zone have become progressively more numerous since the importance of assessing possible future sea level rises has become apparent traditionally this has been achieved using a combination of biological and physical indicators e g pollen diatoms foraminifera grain size etc in some circumstances microfossils can be rare or absent from holocene sediments and in these cases carbon isotope ratios 13c and organic carbon to total nitrogen ratios c n can be used because they have the potential to provide information as to the origin of organic material preserved in coastal environments the distinction in 13c and c n of the various sources of carbon to estuarine sediments has led to its wide use as a tracer of carbon pathways and storage in estuaries more recently these techniques have been applied to holocene sediments to decipher changes in palaeocoastal environments and thus position relative to sea level and or palaeoriver discharge which have direct relevance to palaeoclimate this paper reviews the studies that have utilised this technique and explores examples from a wide range of coastal environments saltmarshes estuaries lagoons isolation basins and fjords it also discusses the potential alteration of geochemical signatures as a result of decompositional processes organic matter decomposition has been shown to change sediment 13c and c n values and thus an understanding of the processes involved is necessary in order to have confidence in the palaeoenvironmental interpretation of holocene 13c and c n decompositional shifts in c n and particularly 13c can occur over a relatively short time period however it is the direction of change in 13c and c n rather than absolute values that is key for interpreting changes in relative sea level and thus such changes are commonly preserved

c3 c4 variations in salt marsh sediments an application of compound specific isotopic analysis of lipid biomarkers to late holocene paleoenvironmental research in salt marshes bulk carbon isotope values reflect organic matter contributions not only from salt marsh plants but also from algal and bacterial inputs as well as allochthonous terrestrial organic matter in the present study compound specific isotope analysis was applied to a core and modern plant samples collected from a machiasport maine salt marsh we sampled 10 plant species common to the marsh including spartina alterniftora spartina patens juncus gerardi solidago sempervirens salicornia europa potentilla anserina atriplex patula plantago maritima suaeda maritima and limonium nashii isolation of two n alkanes c 27 and c 29 present in marsh plant samples allowed for the reconstruction of past plant communities present in the cored deposits for the c 27 and c 29 homologues there is a 3 10 separation in carbon isotopic composition between c3 and c4 species carbon isotopic values down core show a transition from a c4 dominated plant community to a c3 dominated community attributable to the migration of lower marsh zones onto brackish freshwater marsh zones during a late holocene relative sea level rise the two homologues used have the potential to provide paleoenvironmental information in future core work where the sea level variable will be controlled

sedimentary and foraminiferal evidence of the 2011 tōhoku oki tsunami on the sendai coastal plain japan abstract the 2011 t hoku oki megathrust earthquake mw 9 0 generated a tsunami that reached the sendai coastal plain with flow heights of 2 to 11 m above tp tokyo peil we examined the tsunami deposit exposed in 14 shallow trenches along a 4 5 km transect perpendicular to the coast we primarily document the stratigraphical sedimentological foraminiferal and geochemical characteristics of the t hoku oki tsunami deposit and perform a preliminary comparison with sediments deposited by the j gan tsunami of a d 869 in the coastal forest and rice fields inundated by the t hoku oki tsunami a poorly sorted dark brown soil is buried by a poorly sorted brown medium grained sand deposit in some trenches located more than 1 2 km inland the sand is capped by a thin muddy sand layer the tsunami deposit although highly variable in thickness is generally thickest 25 cm near the coastal dune and thins to less than 5 mm at 4 5 km inland the tsunami deposit was discriminated from the underlying soil by the appearance of recent and fossil foraminifera and a pronounced increase in grain size that fined upward and landward the recent foraminifera preserved in the sandy facies of the deposit are rare and showed evidence of prolonged subaerial exposure e g pitting corrosion fragmentation recent foraminifera likely originated from coastal dune and beach sediments that were breached by the tsunami calcified and sediment in filled fossil foraminifera are abundant and were eroded from sedimentary units and transported by fluvial or wave activity to sendai bay trends associated with test size e g decreasing concentration of large test sizes with distance inland are in agreement with grain size data at two locations a decrease in total organic carbon and an increase in 13c were found in the tsunami sand compared with the underlying soil supporting a beach to intertidal origin for the upper unit

bedload entrainment travel lengths step lengths rest periods studied with passive iron magnetic and active radio tracer techniques this paper reports results from bedload transport investigations with active radio and passive iron magnetic tracers in the lainbach a step pool mountain river in bavaria southern germany the spatial distributions of the iron tracers after flood events can be best described by exponential or gamma distributions there is some indication of a tendency of size selective transport of the iron tracers but there is also a considerable amount of scatter in the correlations between weight size and travel length owing to the masking influence of other variables such as the shape of the particles and different positions in the river bed the experiments with artificial magnetic tracers showed that elongated pebbles rods had the longest mean transport distance platy ones discs remained relatively close to the starting points the particles from the pool showed the greatest transport lengths and a 100 per cent chance of being eroded the pebble transmitter system petsy consists of transmitters implanted into individual pebbles a computerized receiver a stationary antenna system with an antenna switchboard and a data logging system the particles do not move continuously but in a series of transport steps and non movement intervals a single value for a given size class is not adequate to describe the critical conditions of entrainment under natural circumstances a probability approach is much more suitable the critical unit discharges total discharge divided by active channel width along the measuring reach are dependent on river bed morphology in the steps bedload needs higher unit discharges to be entrained once entrained the transport of bedload is stochastic in nature and the single particle transport is controlled by the step lengths and the duration of rest periods the distributions of both parameters can be approximated by exponential functions applying the stochastic concept proposed by einstein the mean values of the random variables step length and duration of rest period measured with the petsy technique were used for the simulation of spatial distributions of bedload particles from point sources more field and laboratory data are needed to include varying flow and roughness conditions with tracers representing different particle characteristics

investigating the record of permian climate change from argillaceous sedimentary rocks oman a standard method for the analysis of carbon isotope composition of bulk organic matter 13 c bulk in palaeoenvironmental and stratigraphic studies of sedimentary basins associated with hydrocarbons is suggested this method includes the removal of interstitial hydrocarbon within the sediments which is shown to have a negative effect on 13 c using the method a 13 c bulk trend c 21 to 24 was found within the lower permian al khlata and lower gharif formations of thuleilat 16 and 42 well sections south oman palaeontological and sedimentological evidence indicates considerable palaeoenvironmental change from a cold climate lowland fern flora and upland primitive conifer flora low in the sequence to a lowland cycad like and upland glossopterid or other gymnospermous flora higher in the sequence the lithologies range from glacial diamictite at the base to calcrete horizons and redbeds at the top it is therefore likely that the 13 c bulk trend is related to palaeoenvironmental change

middle to late holocene fluctuations of c3 and c4 vegetation in a northern new england salt marsh sprague marsh phippsburg maine abstract a 3 1 m sediment core was analyzed for stable carbon isotope composition of organic matter and higher plant leaf wax hplw lipid biomarkers to determine holocene shifts in c 3 higher high marsh and c 4 low and or high marsh plant deposition at the sprague river salt marsh phippsburg maine the carbon isotope composition of the bulk sediment and the hplw parallel each other throughout most of the core suggesting that terrestrial plants are an important source of organic matter to the sediments and diagenetic alteration of the bulk sediments is minimal the current salt marsh began to form 2500 cal yr bp low and or high c 4 marsh plants dominated deposition at 2000 cal yr bp 700 cal yr bp and for the last 200 cal yr bp expansion of higher high marsh c 3 plants occurred at 1300 and 600 cal yr bp these major vegetation shifts result from a combination of changes in relative sea level rise and sediment accumulation rates average annual carbon sequestration rates for the last 2500 years approximate 40 g c yr 1 m 2 and are in strong agreement with other values published for the gulf of maine given that maine salt marshes cover an area of 79 km 2 they represent an important component of the terrestrial carbon sink more detailed isotopic and age records from a network of sediment cores at sprague marsh are needed to truly evaluate the long term changes in salt marsh plant communities and the impact of more recent human activity including global warming on salt marsh vegetation

modern foraminifera δ13c and bulk geochemistry of central oregon tidal marshes and their application in paleoseismology we assessed the utility of 13c and bulk geochemistry total organic content and c n to reconstruct relative sea level changes on the cascadia subduction zone through comparison with an established sea level indicator benthic foraminifera four modern transects collected from three tidal environments at siletz bay oregon usa produced three elevation dependent groups in both the foraminiferal and 13c bulk geochemistry datasets foraminiferal samples from the tidal flat and low marsh are identified by miliammina fusca abundances of 45 middle and high marsh by m fusca abundances of 25 the 13c values from the groups defined with 13c bulk geochemistry analyses decrease with an increasing elevation 24 1 1 7 in the tidal flat and low marsh 27 3 1 4 in the middle and high marsh and 29 6 0 8 in the highest marsh samples we applied the modern foraminiferal and 13c distributions to a core that contained a stratigraphic contact marking the great cascadia earthquake of ad 1700 both techniques gave similar values for coseismic subsidence across the contact 0 88 0 39 m and 0 71 0 56 m suggesting that 13c has potential for identifying amounts of relative sea level change due to tectonics

distribution of modern salt marsh foraminifera in the albemarle pamlico estuarine system of north carolina usa implications for sea level research abstract we described the distributions of foraminifera from ten physiographically distinct salt marshes in the albemarle pamlico estuarine system north carolina using 193 surface samples we defined elevation dependent ecological zones at individual sites using cluster analysis and detrended correspondence analysis additionally seven principal biozones of salt marsh foraminifera were identified that have distinctive spatial distributions reflecting a pattern of salinity regimes caused by the current configuration of barrier island inlets high salinity sites along the southern outer banks are associated with sub tidal calcareous assemblages low marshes dominated by miliammina fusca and high marsh environments defined by haplophragmoides wilberti trochammina inflata and arenoparrella mexicana in contrast lower salinity marshes have ammobaculites spp in sub tidal settings miliammina fusca dominated low marshes and high marsh settings characterized by jadammina macrescens spatial variation of foraminiferal populations and the potential for biozones to migrate in response to changing inlet configuration and salinity suggests that datasets of modern salt marsh foraminifera from multiple environments would be appropriate for reconstructing holocene relative sea level in north carolina

late holocene δ13c and pollen records of paleosalinity from tidal marshes in the san francisco bay estuary california abstract records of stable carbon isotopes 13c are presented from cores collected from four san francisco bay marshes and used as a proxy for changes in estuary salinity the 13c value of organic marsh sediments are a reflection of the relative proportion of c3 vs c4 plants occupying the surface and can thus be used as a proxy for vegetation change on the marsh surface the four marshes included in this study are located along a natural salinity gradient that exists in the san francisco bay and records of vegetation change at all four sites can be used to infer changes in overall estuary paleosalinity the 13c values complement pollen data from the same marsh sites producing a paleoclimate record for the late holocene period in the san francisco bay estuary the data indicate that there have been periods of higher than average salinity in the bay estuary reduced fresh water inflow including 1600 1300 cal yr b p 1000 800 cal yr b p 300 200 cal yr b p and ca a d 1950 to the present periods of lower than average salinity increased fresh water inflow occurred before 2000 cal yr b p from 1300 to 1200 cal yr b p and ca 150 cal yr b p to a d 1950 a comparison of the timing of these events with records from the california coast watershed and beyond the larger drainage of the bay reveals that the paleosalinity variations reflected regional precipitation

carbon isotope diatom and pollen evidence for late holocene salinity change in a brackish marsh in the san francisco estuary analysis of diatoms pollen and the carbon isotopic composition of a sediment core from a brackish marsh in the northern part of the san francisco estuary has provided a paleosalinity record that covers the past 3000 yr changes in marsh composition and diatom frequencies are assumed to represent variations in freshwater inflow to the estuary three periods of relatively high salinity low freshwater inflow are indicated 3000 to 2500 cal yr b p 1700 to 730 cal yr b p and ca a d 1930 to the present the most recent period of high salinity is primarily due to upstream storage and water diversion within the sacramento san joaquin watershed although drought may also have been a factor the two earlier high salinity periods are likely the result of reduced precipitation low salinity high freshwater flow is indicated for the period 750 cal yr b p to a d 1930 c 2001 university of washington

quantifying geomorphic change at ephemeral stream restoration sites using a coupled model approach abstract rock detention structures are used as restoration treatments to engineer ephemeral stream channels of southeast arizona usa to reduce streamflow velocity limit erosion retain sediment and promote surface water infiltration structures are intended to aggrade incised stream channels yet little quantified evidence of efficacy is available the goal of this 3 year study was to characterize the geomorphic impacts of rock detention structures used as a restoration strategy and develop a methodology to predict the associated changes we studied reaches of two ephemeral streams with different watershed management histories one where thousands of loose rock check dams were installed 30 years prior to our study and one with structures constructed at the beginning of our study the methods used included runoff sediment transport and geomorphic modelling and repeat terrestrial laser scanner tls surveys to map landscape change where discharge data were not available event based runoff was estimated using kineros2 a one dimensional kinematic wave runoff and erosion model discharge measurements and estimates were used as input to a two dimensional unsteady flow and sedimentation model nays2dh that combined a gridded flow transport and bed and bank simulation with geomorphic change through comparison of consecutive dems the potential to substitute uncalibrated models to analyze stream restoration is introduced we demonstrate a new approach to assess hydraulics and associated patterns of aggradation and degradation resulting from the construction of check dams and other transverse structures notably we find that stream restoration using rock detention structures is effective across vastly different timescales

carbon stable isotope δ13c and elemental toc tn geochemistry in saltmarsh surface sediments western brittany france a useful tool for reconstructing holocene relative sea level providing a dense network of holocene relative sea level rsl records still faces some challenges such as the paucity of microfossil assemblages within some holocene sedimentary sequences recently the isotopic 13c and elemental geochemistry total organic carbon toc total nitrogen tn and c n ratios of saltmarsh sediments has showed potential for rsl reconstruction this study presents the results of new 13c toc and tn measurements obtained on surface sediments of two marshes of the brittany region france overall the distribution of 13c toc tn and c n values shows clear dependencies with elevation sediments from above and below the high tide level show contrasting tn contents clustering analyses identified three elevation dependent groups characterized by specific values of 13c toc and tn the use of this geochemical reference for rsl reconstruction is tested on a core retrieved from one of the marshes the sea level index points obtained plot in good accordance with the microfauna based rsl positions previously obtained in the region some diagenetic losses in tn are observed between modern and holocene sediments this does not appear to be harmful to the accuracy of the rsl reconstructions but suggests that c n ratios may be unreliable palaeoenvironmental proxies in this specific context

taphonomy of salt marsh foraminifera an example from coastal georgia abstract in salt marshes of st catherines island georgia total foraminiferal density decreases significantly within the top 10 cm of marsh sediment selective preservation impacts both calcareous and agglutinated taxa calcareous taxa are removed through dissolution and agglutinated ones through bacterial degradation of cements or predation shallow to deep infaunal taxa generally are the most likely to be preserved although miliammina fusca and ammotium spp all epifaunal to shallow or intermediate infaunal dwellers have cements that are highly susceptible to degradation in southeastern u s marshes total foraminiferal density in both surface and subsurface sediment is higher in the low marsh than either the transitional or high marsh zones selective preservation and downcore enrichment by some infaunal taxa alters the percent abundance of some paleoenvironmentally significant taxa in subsurface assemblages the best baseline for paleoenvironmental studies using salt marsh foraminifera in these settings is not the marsh surface 0 1 cm but rather assemblages preserved 10 cm below the marsh surface

stratigraphic record of holocene coseismic subsidence padang west sumatra 1 stratigraphic evidence is found for two coseismic subsidence events that underlie a floodplain 20 km south of padang west sumatra along the mentawai segment 0 5 s 0 3 s of the sunda subduction zone each earthquake is marked by a sharp soil mud contact that represents a sudden change from mangrove to tidal flat the earthquakes occurred about 4000 and 3000 cal years b p based on radiocarbon ages of detrital plant fragments and seeds the absence of younger paleoseismic evidence suggests that late holocene relative sea level fall left the floodplain too high for an earthquake to lower it into the intertidal zone our results point to a brief few thousand year window of preservation of subsidence events in tidal wetland stratigraphic sequences a result that is generally applicable to other emergent coastlines of west sumatra

velocity characteristics along a small step pool channel this paper summarizes measurements of velocity along three reaches of a small mountain channel with step pool bedforms a one dimensional electromagnetic current meter was used to record velocity fluctuations at 37 fixed measurement points during five measurement intervals spanning the peak of the annual snowmelt hydrograph measurement cross sections were located upstream from a bed step at the step lip downstream from the step and in a uniform gradient run data analyses focused on characteristics of velocity profiles and on correlations between velocity characteristics and the potential control variables bedform type reach gradient and flow depth to test the hypothesis that velocity characteristics are related to channel bedform types anova and ancova tests were performed for the average velocity and coefficient of variation of point velocity data results indicate that high frequency velocity variations correlate to some degree with both channel characteristics and discharge velocity became more variable as stage increased particularly at low gradient reaches with less variable bed roughness velocity profiles suggest that locations immediately downstream from bed steps are dominated by wake turbulence from mid profile shear layers locations immediately upstream from steps at step lips and in runs are dominated by bed generated turbulence adverse pressure gradients upstream and downstream from steps may be enhancing turbulence generation whereas favourable pressure gradients at steps are suppressing turbulence the bed generated turbulence and skin friction of runs appear to be less effective energy dissipators than the wake generated turbulence and form drag of step pool bedforms copyright 2000 john wiley sons ltd

bedload transport in the instrumented catchment of the rio cordon part ii analysis of the bedload rate abstract sediment transport is monitored by a specially designed instrumentation installed on a steep mountain streams the rio cordon the variability of bedload rate and yield reflects the variability in flow discharge bedload and flow data for ordinary low peak flow floods and exceptional sediment transport events are used to test the range of application of the bedload equations proposed for high gradient streams such equations overestimate bedload rate for ordinary events while their reliability increases when used to predict high bedload transport rates like those recorded during the exceptional flood that affected rio cordon on september 14 1994 the best agreement between computed and measured values of cumulated bedload volumes is found by using the bagnold bagnold r a 1956 the flow of cohesionless grains in fluids philos trans r soc london 249a 235 297 smart and jaeggi smart j m jaeggi m n r 1983 sediment transport on steep slopes mitteil 64 versuchsanstalt fur wasserbau hydrologie und glaziologie eth zurich switzerland 191 pp and rickenmann rickenmann d 1991 hyperconcentrated flow and sediment transport at steep slopes j hydraul eng zurig 117 11 1419 1439 formulas the schoklitsch equation schoklitsch a 1962 handbuch des wasserbaues 3rd edn springer wien also provides good estimations for instantaneous bedload rates at high sediment transport intensity and unlimited sediment supply conditions the formal type of the last equation is still valid and can be calibrated for low intensity bedload rates

environmental factors controlling spatial variation in sediment yield in a central andean mountain area a large spatial variability in sediment yield was observed from small streams in the ecuadorian andes the objective of this study was to analyze the environmental factors controlling these variations in sediment yield in the paute basin ecuador sediment yield data were calculated based on sediment volumes accumulated behind checkdams for 37 small catchments mean annual specific sediment yield ssy shows a large spatial variability and ranges between 26 and 15 100 mg km 2 year 1 mean vegetation cover c fraction in the catchment i e the plant cover at or near the surface exerts a first order control on sediment yield the fractional vegetation cover alone explains 57 of the observed variance in ln ssy the negative exponential relation ssy a x e b c which was found between vegetation cover and sediment yield at the catchment scale 10 3 10 9 m 2 is very similar to the equations derived from splash interrill and rill erosion experiments at the plot scale 1 10 3 m 2 this affirms the general character of an exponential decrease of sediment yield with increasing vegetation cover at a wide range of spatial scales provided the distribution of cover can be considered to be essentially random lithology also significantly affects the sediment yield and explains an additional 23 of the observed variance in ln ssy based on these two catchment parameters a multiple regression model was built this empirical regression model already explains more than 75 of the total variance in the mean annual sediment yield these results highlight the large potential of revegetation programs for controlling sediment yield they show that a slight increase in the overall fractional vegetation cover of degraded land is likely to have a large effect on sediment production and delivery moreover they point to the importance of detailed surface vegetation data for predicting and modeling sediment production rates c 2007 elsevier b v all rights reserved

late holocene sedimentation and hydrologic development in a shallow coastal sinkhole on great abaco island the bahamas abstract it remains poorly understood how sea level drives environmental change and hydrographic development in coastal karst basins underwater caves sinkholes blueholes etc over millennial timescales it was previously hypothesized that coastal karst basins ckbs transition from vadose to littoral then anchialine and finally submarine environments as sea level rise inundates coastal karst landscapes but the initial flooding event of ckbs remains challenging to sample runway sinkhole hosts a modern anchialine ecosystem located 225 m from great abaco island coastline in the bahamas and its shallow water depth 1 8 mbsl permits an investigation into the early environmental evolution and hydrographic development in a ckbs after inundation by sea level rise four sediment cores were collected from runway sinkhole and late holocene environmental change was reconstructed with benthic foraminiferal paleoecology organic matter geochemistry om 13 c org and c n x radiography and radiocarbon dating despite some uncertainties associated with the chronology it appears that holocene sea level rise initially flooded runway sinkhole and created a littoral environment at least by 3 9 ka whereafter a detrital peat deposit accumulated in the sinkhole this detrital peat had a high organic matter content mean 88 a 13 c org value indicative of organic matter derived from c 3 plants including mangroves 28 and an unknown calcareous microfossil suggestive of a non marine habitat in the sinkhole a shift to carbonate sand deposition organic matter with more marine influenced 13 c org values 23 and expansion of euryhaline bolivina striatula elphidium poeyanum and triloculina bermudezi and anchialine physalidia simplex and conicospirillina exleyi benthic foraminifera at 1 2 ka marks the onset of modern anchialine environmental conditions at the sediment water interface 1 8 mbsl these results suggest that relative sea level rise in the bahamas forced environmental change in runway sinkhole at 1 2 ka and indicate that peat deposits in coastal sinkholes must be verified as in situ before being utilized as sea level indicators

channel reach morphology in mountain drainage basins a classification of channel reach morphology in mountain drainage basins synthesizes stream morphologies into seven distinct reach types colluvial bedrock and five alluvial channel types cascade step pool plane bed pool rime and dune ripple coupling reach level channel processes with the spatial arrangement of reach morphologies their links to hillslope processes and external forcing by confinement ripar ian vegetation and woody debris defines a process based framework within which to assess channel condition and response potential in mountain drainage basins field investigations demonstrate character istic slope grain size shear stress and roughness ranges for different reach types observations consistent with our hypothesis that alluvial channel morphologies reflect specific roughness configurations ad justed to the relative magnitudes of sediment supply and transport ca pacity steep alluvial channels cascade and step pool have high ratios of transport capacity to sediment supply and are resilient to changes in discharge and sediment supply whereas low gradient alluvial channels pool rime and dune ripple have lower transport capacity to supply ra tios and thus exhibit significant and prolonged response to changes in sediment supply and discharge general differences in the ratio of transport capacity to supply between channel types allow aggregation of reaches into source transport and response segments the spatial distribution of which provides a watershed level conceptual model linking reach morphology and channel processes these two scales of channel network classification define a framework within which to in vestigate spatial and temporal patterns of channel response in moun tain drainage basins

coastal subsidence in oregon usa during the giant cascadia earthquake of ad 1700 quantitative estimates of land level change during the giant ad 1700 cascadia earthquake along the oregon coast are inferred from relative sea level changes reconstructed from fossil foraminiferal assemblages preserved within the stratigraphic record a transfer function based upon a regional training set of modern sediment samples from oregon estuaries is calibrated to fossil assemblages in sequences of samples across buried peat mud and peat sand contacts marking the ad 1700 earthquake reconstructions of sample elevations with sample specific errors estimate the amount of coastal subsidence during the earthquake at six sites along 400 km of coast the elevation estimates are supported by lithological carbon isotope and faunal tidal zonation data coseismic subsidence at nehalem river nestucca river salmon river alsea bay siuslaw river and south slough varies between 0 18 m and 0 85 m with errors between 0 18 m and 0 32 m these subsidence estimates are more precise consistent and generally lower than previous semi quantitative estimates following earlier comparisons of semi quantitative subsidence estimates with elastic dislocation models of megathrust rupture during great earthquakes our lower estimates for central and northern oregon are consistent with modeled rates of strain accumulation and amounts of slip on the subduction megathrust and thus with a magnitude of 9 for the ad 1700 earthquake

step pool evolution in the rio cordon northeastern italy the principle that formative events punctuated by periods of evolution recovery or temporary periods of steady state conditions control the development of the step pool morphology has been applied to the evolution of the rio cordon stream bed the rio cordon is a small catchment 5 km2 within the dolomites wherein hydraulic parameters of floods and the coarse bedload are recorded detailed field surveys of the step pool structures carried out before and after the september 1994 and october 1998 floods have served to illustrate the control on step pool changes by these floods floods were grouped into two categories the first includes ordinary events which are characterized by peak discharges with a return time of one to five years 1 8 5 15 m3 s 1 and by an hourly bedload rate not exceeding 20 m3 h 1 the second refers to exceptional events with a return time of 30 50 years a flood of this latter type occurred on 14 september 1994 with a peak discharge of 10 4 m3 s 1 and average hourly bedload rate of 324 m3 h 1 step pool features were characterized primarily by a steepness parameter c h ls s the evolution of the steepness parameter was measured in the field from 1992 to 1998 the results indicate that maximum resistance conditions are gradually reached at the end of a series of ordinary flood events during this period bed armouring dominate the sediment transport response however following an extraordinary flood and unlimited sediment supply conditions the steepness factor can suddenly decrease as a result of sediment trapped in the pools and a lengthening of step spacing the analogy of step spacing with antidune wavelength and the main destruction and transformation mechanism of the steps are also discussed copyright 2001 john wiley sons ltd

a field investigation of the influence of sediment supply on step pool morphology and stability abstract the effect of the sediment supply on step pool morphology and stability was studied through the investigation of 42 step pool reaches eight in the vosges and 34 in the alps france step pool geometry step wavelength l and height h was measured for each reach and the data set split into two distinct groups comprising 25 connected to a sediment source step pool reaches and 17 disconnected step pool reaches the geometry analysis showed differences between the two groups with the shape factors k l hr and the h hr ratios hr is the residual pool depth being lower for disconnected step pools this was interpreted to result from progressively changing geometry over time with disconnected step pool geometry defining the probable asymptotic characteristic associated with this long term process the measured step pool dimensions were in good agreement with equations based on maximum flow resistance abrahams et al 1995 energy of a falling jet comiti et al 2005 and channel spanning deposition chartrand et al 2011 however the average shape factor for the comiti et al equation was k 17 instead of 8 as the authors had proposed the data set was extended to 255 values with data from the literature which confirmed this average value for k field evidence moss cover and stone imbrication indicate that connected step pools are mobile whereas disconnected step pools are stable this was investigated by a hydraulic analysis of threshold motion conditions for the boulder steps comparison with discharges measured at nearby gauging stations indicates that remobilization return periods are 20 50 years for connected step pools and even less when considering scouring effects and greater than 50 years for disconnected step pools this difference in step mobility was ascribed to the fact that with sediment supply the channel can freely adjust its local slope allowing a relatively efficient transfer downstream of large boulders by scouring effects

the application of δ13c toc and c n geochemistry of mangrove sediments to reconstruct holocene paleoenvironments and relative sea levels puerto rico abstract we assessed the use of 13c toc and c n values of bulk sedimentary organic matter om to reconstruct paleoenvironmental and relative sea level change from mangrove environments in puerto rico the modern distribution of 13c toc and c n values was described from 63 vegetation and 59 surface sediment samples collected from three sites containing basin and riverine mangrove stands and was compared to microfossil foraminiferal and thecamoebian assemblages four vertically zoned environments were identified tidal flat 13c 18 6 2 8 toc 10 2 5 7 c n 12 7 3 1 mangrove 13c 26 4 1 0 toc 33 9 13 4 c n 24 3 6 2 brackish transition 13c 28 8 0 7 toc 40 8 11 7 c n 21 7 3 7 and freshwater swamp 13c 28 4 0 4 toc 42 8 4 8 c n 17 0 1 1 these environments had distinct 13c toc and c n values with the exception of the brackish transition and freshwater swamp zones that were difficult to distinguish on a geochemical basis alone the foraminiferal assemblages were complicated by a group that did not show a relationship to elevation due to the presence of calcareous foraminifera occurring above mean higher high water mhhw likely resulting from washover or transport by storms however the ratio of foraminifera to thecamoebians f t along with 13c toc and c n values refines the distinction between brackish and freshwater environments using linear discriminant analysis we applied the 13c toc c n and f t distributions to a 1 7 m core containing a continuous sequence of rhizophora mangle peat which began accumulating at 1650 1930 ce together microfossils 13c toc and c n values and the core chronology from 137cs and radiocarbon dating revealed that sediments in the core likely accumulated in response to anthropogenic sediment delivery making it unsuitable for relative sea level reconstruction we caution that in the absence of detailed litho bio chemo or chrono stratigraphic analyses as presented here care should be taken in interpreting sea level histories derived from single dates on mangrove peats

testing the use of bulk organic δ13c δ15n and corg ntot ratios to estimate subsidence during the 1964 great alaska earthquake abstract during the m w 9 2 1964 great alaska earthquake turnagain arm near girdwood alaska subsided 1 7 0 1 m based on pre and postearthquake leveling the coseismic subsidence in 1964 caused equivalent sudden relative sea level rsl rise that is stratigraphically preserved as mud over peat contacts where intertidal silt buried peaty marsh surfaces changes in intertidal microfossil assemblages across these contacts have been used to estimate subsidence in 1964 by applying quantitative microfossil transfer functions to reconstruct corresponding rsl rise here we review the use of organic stable c and n isotope values and c org n tot ratios as alternative proxies for reconstructing coseismic rsl changes and report independent estimates of subsidence in 1964 by using 13 c values from intertidal sediment to assess rsl change caused by the earthquake we observe that surface sediment 13 c values systematically decrease by 4 over the 2 5 m increase in elevation along three 60 to 100 m long transects extending from intertidal mud flat to upland environments we use a straightforward linear regression to quantify the relationship between modern sediment 13 c values and elevation n 84 r 2 0 56 the linear regression provides a slope intercept equation used to reconstruct the paleoelevation of the site before and after the earthquake based on 13 c values in sandy silt above and herbaceous peat below the 1964 contact the regression standard error average 0 59 reflects the modern isotopic variability at sites of similar surface elevation and is equivalent to an uncertainty of 0 4 m elevation with respect to mean higher high water to reduce potential errors in paleoelevation and subsidence estimates we analyzed multiple sediment 13 c values in nine cores on a shore perpendicular transect at bird point our method estimates 1 3 0 4 m of coseismic rsl rise across the 1964 contact by taking the arithmetic mean of the differences n 9 between reconstructed elevations for sediment above and below the 1964 earthquake subsidence contact this estimate compares well with independent subsidence estimates derived from post earthquake leveling in turnagain arm and from microfossil transfer functions at girdwood 1 50 0 32 m while our results support the use of bulk organic 13 c for reconstructing rsl change in southern alaska the variability of stable isotope values in modern and buried intertidal sediment required the analysis of multiple samples to reduce error

extended late holocene relative sea level histories for north carolina usa abstract we produced 3000 year long relative sea level rsl histories for two sites in north carolina usa using foraminifera preserved in new and existing cores of dated salt marsh sediment at cedar island rsl rose by 2 4 m during the past 3000 years compared to 3 3 m at roanoke island this spatial difference arises primarily from differential gia that caused late holocene rsl rise to be 0 1 0 2 mm yr faster at roanoke island than at cedar island however a non linear difference in rsl between the two study regions particularly from 0 ce to 1250 ce indicates that additional local to regional scale processes drove centennial scale rsl change in north carolina therefore the cedar island and roanoke island records should be considered as independent of one another between site differences on sub millennial timescales cannot be adequately explained by non stationary tides sediment compaction or local sediment dynamics we propose that a period of accelerating rsl rise from 600 ce to 1100 ce that is present at roanoke island and other sites north of cape hatteras at least as far as connecticut but absent at cedar island and other sites south of cape hatteras at least as far as northeastern florida is a local to regional scale effect of dynamic ocean and or atmospheric circulation

stable carbon isotopes as potential sea level indicators in salt marshes north carolina usa we compared the use of 13c values and c n ratios from salt marsh sediments to reconstruct relative sea level rsl with an established approach using foraminifera analysis of bulk organic sediment and plant samples collected along transects at two sites in north carolina usa demonstrates that sediment 13c values can be used to distinguish between spartina alterniflora dominated low marsh c photosynthetic pathway 13c values from 17 6 to 16 1 and juncus roemerianus dominated high marsh c 3 photosynthetic pathway 13c values from 28 2 to 21 8 environments juncus roemerianus plants undergo little decompositional change in 13c average 0 8 although there is a clear difference between spartina alterniflora tissue and bulk organic sediments approximately 4 c n ratios on bulk organic sediment from freshwater upland and salt marsh environments converge during early diagenesis rendering them of little use in reconstructing rsl the utility of 13c values as a sea level indicator is limited by the elevational range of c4 plants making it difficult to recognize salt marsh subenvironments and improve the precision of rsl reconstructions furthermore juncus roemerianus dominated high marsh and freshwater upland sediments cannot be adequately distinguished with 13c values

the application of δ13c toc and c n geochemistry to reconstruct holocene relative sea levels and paleoenvironments in the thames estuary uk we examined the use of d 13 c toc and c n geochemistry of sedimentary organic matter to reconstruct former sea levels and paleoenvironments in the absence of suitable microfossil data the modern distribution of d 13 c toc and c n of 33 vegetation and 74 surface sediment samples collected from four coastal wetlands in the thames estuary and norfolk uk are described the d 13 c toc and c n geochemistry of sediments varied in relation to the input of in situ vascular vegetation versus allochthonous particulate organic matter and algae which was controlled primarily by tidal inundation we reviewed published and unpublished studies to produce an english database of vegetation n 257 and sediment n 132 d 13 c toc and c n geochemistry four elevation dependent environments in the database had statistically distinct d 13 c toc and c n values 1 tidal flat low marsh d 13 c 24 9 1 2 toc 3 6 1 7 c n 9 9 0 8 2 middle marsh high d 13 c 26 2 1 0 toc 9 8 6 7 c n 12 1 1 8 3 reed swamp d 13 c 27 9 0 7 toc 36 5 11 5 c n 13 9 1 2 and 4 fen carr d 13 c 29 0 0 6 toc 41 6 5 7 c n 17 4 3 1 the d 13 c toc and c n geochemistry database was applied to a holocene sediment core collected from the thames estuary to produce three new sea level index points and one limiting date illustrating the utility of d 13 c toc and c n values to reconstruct holocene relative sea levels copyright 2015 john wiley sons ltd

sources and preservation of organic matter in plum island salt marsh sediments ma usa long chain n alkanes and stable carbon isotope compositions elemental toc tn c n and stable carbon isotopic delta 13 c compositions and n alkane nc 16 38 concentrations were measured for spartina alterniflora a c 4 marsh grass typha latifolia a c 3 marsh grass and three sediment cores collected from middle and upper estuarine sites from the plum island salt marshes our results indicated that the organic matter preserved in the sediments was highly affected by the marsh plants that dominated the sampling sites delta 13 c values of organic matter preserved in the upper fresh water site sediment were more negative 23 0 0 3 as affected by the c 3 plants than the values of organic matter preserved in the sediments of middle 18 9 0 8 and mud flat sites 19 4 0 1 as influenced mainly by the c4 marsh plants the distribution of n alkanes measured in all sediments showed similar patterns as those determined in the marsh grasses s alterniflora and t latifolia and nc 21 to nc 33 long chain n alkanes were the major compounds determined in all sediment samples the strong odd to even carbon numbered n alkane predominance was found in all three sediments and nc 29 was the most abundant homologue in all samples measured both delta 13 c compositions of organic matter and n alkane distributions in these sediments indicate that the marsh plants could contribute significant amount of organic matter preserved in plum island salt marsh sediments this suggests that salt marshes play an important role in the cycling of nutrients and organic carbon in the estuary and adjacent coastal waters c 2003 elsevier ltd all rights reserved

living foraminifera and total populations in salt marsh peat cores kelsey marsh clinton ct and the great marshes barnstable ma common species of intertidal agglutinated benthic foraminifera in salt marshes in massachusetts and connecticut live predominantly at the marsh surface and in the topmost sediment o 2 5 cm but a considerable part of the fauna lives at depths of 2 5 15 cm few specimens are alive at depths of 15 25 cm with rare individuals alive between 25 50 cm in the sediments specimens living between the sediment surface and 25 cm deep occur in all marsh settings whereas specimens living deeper than 25 cm are restricted to cores from the lower and middle marsh and have an irregular distribution with depth lower and middle marsh areas are bioturbated by metazoa suggesting that living specimens reach these depths at least in part by bioturbation high marsh sediments in new england consist of very dense mats of spa m paleens or distichlis spicatu roots and are not bioturbated by metazoa in this marsh region bioturbation by plant roots and vertical fluid motion may play a role in moving the foraminifera into the sediment the depth distribution of living specimens varies with species living specimens of trochammina injluta consistently occur at the deepest levels this suggests that species have differential rates of survival in the sediment possibly because of differential adaptation to severe dysoxia to anoxia or because of differing food preferences there is no simple correlation between depth in core and faunal diversity absolute abundance and species composition of the assemblages it is therefore possible to derive a signal of fauna1 changes and thus the environmental changes that may have caused them from the complex fauna1 signal of fossil assemblages 0 1998 elsevier science b v all rights reserved

application of stable carbon isotopes for reconstructing salt marsh floral zones and relative sea level new jersey usa we investigated use of 13c in bulk organic sediment to define the botanical origin of samples preserved in coastal sediment as a means to reconstruct relative sea level in new jersey usa modern transects at three sites demonstrated that low and high salt marsh floral zones dominated by c4 species spartina alterniflora and spartina patens were associated with sediment 13c values between 18 9 and 15 8 and occurred from mean tide level mtl to mean higher high water mhhw brackish transitional settings vegetated by phragmites australis with iva fructescens and typha sp c3 species and freshwater upland samples c3 species were characterized by bulk sediment 13c values of 27 0 to 22 0 and existed above mhhw parallel transects at one site suggested that intra site variability was not discernible the utility of 13c values for reconstructing relative sea level in new jersey is limited by an inability to differentiate between brackish sediments related to sea level and freshwater upland samples to facilitate this distinction in a 4 4 m core we used a multi proxy approach 13c values with presence or absence of agglutinated foraminifera to recognize indicative meanings for four sample types sediment with 13c values greater than 18 9 was derived from a vegetated salt marsh and formed between mtl and mhhw sediment with 13c values less than 22 0 and containing agglutinated foraminifera formed in a brackish transitional zone between mhhw and highest astronomical tide hat this is the narrowest elevational range of the four sample types and most precise sea level indicator sediment with 13c values less than 22 0 and lacking foraminifera can only constrain the upper bound of former sea level samples with intermediate values 22 0 to 18 9 formed between mtl and hat using these indicative meanings and radiocarbon dates we suggest that a transition from brackish to salt marsh 13c values recorded in the core took approximately 350 years from 1800 to 1450 cal a bp

utility of salt marsh foraminifera testate amoebae and bulk sediment δ13c values as sea level indicators in newfoundland canada abstract we investigated the utility of foraminifera testate amoebae and bulk sediment 13 c measurements for reconstructing holocene relative sea level from sequences of salt marsh sediment in newfoundland canada modern surface sediment was collected along transects from low to supra tidal elevations in eastern at placentia and western at hynes brook and big river newfoundland consistent with previous work low diversity assemblages of foraminifera display an almost binary division into a higher salt marsh assemblage dominated by jadammina macrescens and balticammina pseudomacrescens and a lower salt marsh assemblage comprised of miliammina fusca this pattern and composition resembles those identified at other high latitude sites with cool climates and confirms that foraminifera are sea level indicators the lowest occurrence of testate amoebae was at approximately mean higher high water the composition of high salt marsh testate amoebae assemblages centropyxis cassis type trinema spp tracheleuglypha dentata type and euglypha spp in newfoundland was similar to elsewhere in the north atlantic but preservation bias favors removal of species with idiosomic tests over those with xenosomic tests the mixed high salt marsh plant community in newfoundland results in bulk surface sediment 13 c values that are typical of c 3 plants making them indistinguishable from freshwater sediment therefore we propose that the utility of this proxy for reconstructing rsl in eastern north america is restricted to the coastline between chesapeake bay and southern nova scotia using a simple multi proxy approach to establish that samples in three radiocarbon dated sediment cores formed between the lowest occurrence of testate amoebae and the highest occurrence of foraminifera we generated three example late holocene sea level index points at hynes brook

carbon and nutrient accumulation in tropical mangrove creeks amazon region abstract the marapanim river estuary mre is part of the amazon estuarine system located in northern brazil which is characterized as having extensive mangrove forests given that previous studies reported co2 and ch4 fluxes from mangrove creeks in this region here we investigate the potential organic carbon sequestration of the creek mudflats to get a better understanding of the carbon cycling through these systems sediment accumulation rates derived from 210pb dating indicated that sampled cores represent the previous 24 4 yr the approximately 24 year total organic carbon toc total nitrogen tn and total phosphorus tp burial rates were estimated to be 192 5 43 5 15 3 4 1 and 3 2 0 8 g m 2 yr 1 respectively a binary source mixing model based on carbon stable isotopes 13c revealed that the sedimentary organic matter om is mainly influenced by marine phytoplankton input 49 to 95 furthermore the toc accumulation rates found here were slightly higher than the global averages estimated for within mangrove forests suggesting that these unaccounted carbon sinks along creek mudflat environments are relevant for carbon budgets in mangrove colonized coastal zones the highest contents stocks and accumulation rates were found in the tidal creek sediments that are most influenced by nearby mangroves and are more protected than sediments from major river margins our results indicate that the creek mudflats play a major role in carbon and nutrients sequestration directly related to grain size and om sources

on the application of contemporary bulk sediment organic carbon isotope and geochemical datasets for holocene sea level reconstruction in nw europe abstract bulk organic stable carbon isotope 13 c and element geochemistry total organic carbon toc and organic carbon to total nitrogen c n analysis is a developing technique in holocene relative sea level rsl research the uptake of this technique in northern europe is limited compared to north america where the common existence of coastal marshes with isotopically distinctive c 3 and c 4 vegetation associated with well defined inundation tolerance permits the reconstruction of rsl in the sediment record in northern europe the reduced range in 13 c values between organic matter sources in c 3 estuaries can make the identification of elevation dependent environments in the holocene sediment record challenging and this is compounded by the potential for post depositional alteration in bulk 13 c values the use of contemporary regional 13 c c n and toc datasets representing the range of physiographic conditions commonly encountered in coastal wetland sediment sequences opens up the potential of using absolute values of sediment geochemistry to infer depositional environments and associated reference water levels in this paper the application of contemporary bulk organic 13 c c n and toc to reconstruct holocene rsl is further explored an extended contemporary regional geochemical dataset of published 13 c c n and toc observations n 142 from tidal dominated c 3 wetland deposits representing tidal flat saltmarsh reedswamp and fen carr environments in temperate nw europe is compiled and procedures implemented to correct for the 13 c suess effect on contemporary 13 c are detailed partitioning around medoids analysis identifies two distinctive geochemical groups in the nw european dataset with tidal flat saltmarsh and reedswamp fen carr environments exhibiting characteristically different sediment 13 c c n and toc values a logistic regression model is developed from the nw european dataset in order to objectively identify in the sediment record geochemical groups and more importantly group transitions thus allowing the altitude of reference water levels to be determined the application of this method in rsl research is demonstrated using the holocene sediments of the mersey estuary uk in which 13 c c n and toc variability is typical of that encountered in holocene sediments from c 3 coastal wetlands in nw europe group membership was predicted with high probability in the depositional contexts studied and the accuracy of group prediction is verified by microfossil evidence the method presented facilitates the application of 13 c c n and toc analysis in rsl reconstruction studies in c 3 vegetated wetlands throughout temperate nw europe

mississippi delta subsidence primarily caused by compaction of holocene strata coastal subsidence causes sea level rise shoreline erosion and wetland loss which poses a threat to coastal populations this is especially evident in the mississippi delta in the southern united states which was devastated by hurricane katrina in 2005 the loss of protective wetlands is considered a critical factor in the extensive flood damage the causes of subsidence in coastal louisiana attributed to factors as diverse as shallow compaction and deep crustal processes remain controversial current estimates of subsidence rates vary by several orders of magnitude here we use a series of radiocarbon dated sediment cores from the mississippi delta to analyse late holocene deposits and assess compaction rates we find that millennial scale compaction rates primarily associated with peat can reach 5mm per year values that exceed recent model predictions locally and on timescales of decades to centuries rates are likely to be 10 mm or more per year we conclude that compaction of holocene strata contributes significantly to the exceptionally high rates of relative sea level rise and coastal wetland loss in the mississippi delta and is likely to cause subsidence in other organic rich and often densely populated coastal plains

degradation of mangrove tissues by arboreal termites nasutitermes acajutlae and their role in the mangrove c cycle puerto rico chemical characterization and organic matter provenance using bulk δ13c c n alkaline cuo oxidation gc ms and solid state 13c nmr 1 arboreal termites are wood decaying organisms that play an important role in the first stages of c cycling in mangrove systems the chemical composition of rhizophora mangle avicennia germinans and laguncularia racemosa leaf stem and pneumatophore tissues as well as associated sediments was compared to that of nests of the termite nasutitermes acajutlae nests gave 13c values of 26 1 to 27 2 0 1 and c n of 43 3 2 0 to 98 6 16 2 which were similar to all stem and pneumatophores but distinct from mangrove leaves or sediments organic matter processed by termites yielded lignin phenol concentrations lambda that were 2 4 times higher than stem or pneumatophores and 10 20 times higher than that of leaves or sediments suggesting that the nests were more resistant to biodegradation than the mangrove vegetation source 13c nmr revealed that polysaccharide content of mangrove tissues 50 69 c was higher than that of the nests 46 51 c conversely lignin accounted for 16 2 19 6 c of nest material a threefold increase relative to living mangrove tissues a similar increase in aromatic methoxyl content was also observed in the nests lipids aliphatic and paraffinic moieties were also important but rather variable chemical components of all three mangrove species representing between 13 5 and 28 3 of the c content termite nests contained 3 14 mg c ha 1 which represents approximately 2 of above ground c storage in mangroves a value that is likely to increase upon burial due to their refractory chemical composition

late quaternary sea level changes and crustal movements in eastern england and eastern scotland an assessment of models of coastal evolution abstract the most comprehensive records of late quaternary coastal environmental change in eastern england and eastern scotland are obtained from the intercalated semi terrestrial peats and intertidal silts clays and sands that have accumulated in estuaries and coastal lowlands radiocarbon dated sea level index points from sites in north east england are evaluated with reference to first a conceptual model of coastal sedimentary environments and second a model of pollen assemblages in holocene coastal environments analysis of these new data indicates differential crustal uplift within north east england of ca 0 2 mm yr for the last 4000 to 5000 radiocarbon years this pattern of uplift is consistent with models of holocene crustal deformation in scotland and england the uplift is attributable to the combined effects of ice unloading and water loading

holocene sea level changes along the north carolina coastline and their implications for glacial isostatic adjustment models abstract we have synthesized new and existing relative sea level rsl data to produce a quality controlled spatially comprehensive database from the north carolina coastline the rsl database consists of 54 sea level index points that are quantitatively related to an appropriate tide level and assigned an error estimate and a further 33 limiting dates that confine the maximum and minimum elevations of rsl the temporal distribution of the index points is very uneven with only five index points older than 4000 cal a bp but the form of the holocene sea level trend is constrained by both terrestrial and marine limiting dates the data illustrate rsl rapidly rising during the early and mid holocene from an observed elevation of 35 7 1 1 m msl at 11062 10576 cal a bp to 4 2 m 0 4 m msl at 4240 3592 cal a bp we restricted comparisons between observations and predictions from the ice 5g vm2 with rotational feedback glacial isostatic adjustment gia model to the late holocene rsl last 4000 cal a bp because of the wealth of sea level data during this time interval the ice 5g vm2 model predicts significant spatial variations in rsl across north carolina thus we subdivided the observations into two regions the model forecasts an increase in the rate of sea level rise in region 1 albemarle currituck roanoke croatan and northern pamlico sounds compared to region 2 southern pamlico core and bogue sounds and farther south to wilmington the observations show late holocene sea level rising at 1 14 0 03 mm year 1 and 0 82 0 02 mm year 1 in regions 1 and 2 respectively the ice 5g vm2 predictions capture the general temporal trend of the observations although there is an apparent misfit for index points older than 2000 cal a bp it is presently unknown whether these misfits are caused by possible tectonic uplift associated with the mid carolina platform high or a flaw in the gia model a comparison of local tide gauge data with the late holocene rsl trends from regions 1 and 2 support the spatial variation in rsl across north carolina and imply an additional increase of mean sea level of greater than 2 mm year 1 during the latter half of the 20th century this is in general agreement with historical tide gauge and satellite altimetry data

influence of spartina and juncus on saltmarsh sediments iii organic geochemistry abstract total organic carbon c n ratios of sediment organic matter and 13c of sediment organic matter 13corg were measured as a function of depth at four sites in a saltmarsh on sapelo island ga during summer 2006 the goal of this study is to assess the sources of sediment organic matter at each site and to investigate the influence of macrophytes and macrofauna on the observed carbon isotopic signatures and c n ratios at each site the four sites include two adjacent creekside sites one densely vegetated by tall form spartina alterniflora and the other mostly unvegetated together with two adjacent sites higher in the marsh including a site with sparse short form spartina and a neighboring site densely vegetated with juncus roemarianus total organic carbon in the sediments of these sites varies between 2 1 and 6 4 with the highest values observed at shallow depths at the unvegetated creek bank and the lowest at the short spartina site c n ratios of the sediment organic matter vary between 10 6 and 17 3 with higher values at the short spartina site compared to the other three sites 13corg varies little with depth averaging 20 1 0 2 at the juncus tall spartina and adjacent unvegetated sites and 17 8 0 6 at the short spartina site mixing calculations completed with the depth averaged c n and 13corg for each site assuming three endmember organic matter sources c3 plants c4 plants phytoplankton suggest that up to 75 of the organic matter at all four sites is derived from phytoplankton surprisingly the average 13corg and c n values and therefore the calculated contributions of the three endmember organic matter sources to the total sediment organic matter are very similar at the juncus tall spartina and unvegetated creekbank sites the greater 13corg and c n of the short spartina sediments is consistent with little or no inclusion of c3 derived organic matter in the sediments at this site in spite of the close proximity to the densely vegetated juncus site and with less degradation of the organic matter compared to the other three sites

late holocene sea and land level change on the u s southeastern atlantic coast abstract late holocene relative sea level rsl reconstructions can be used to estimate rates of land level subsidence or uplift change and therefore to modify global sea level projections for regional conditions these reconstructions also provide the long term benchmark against which modern trends are compared and an opportunity to understand the response of sea level to past climate variability to address a spatial absence of late holocene data in florida and georgia we reconstructed 1 3 m of rsl rise in northeastern florida usa during the past 2600 years using plant remains and foraminifera in a dated core of high salt marsh sediment the reconstruction was fused with tide gauge data from nearby fernandina beach which measured 1 91 0 26 mm year of rsl rise since 1900 ce the average rate of rsl rise prior to 1800 ce was 0 41 0 08 mm year assuming negligible change in global mean sea level from meltwater input removal and thermal expansion contraction this sea level history approximates net land level subsidence and geoid change principally from glacio isostatic adjustment historic rates of rise commenced at 1850 1890 ce and it is virtually certain p 0 99 that the average rate of 20th century rsl rise in northeastern florida was faster than during any of the preceding 26 centuries the linearity of rsl rise in florida is in contrast to the variability reconstructed at sites further north on the u s atlantic coast and may suggest a role for ocean dynamic effects in explaining these more variable rsl reconstructions comparison of the difference between reconstructed rates of late holocene rsl rise and historic trends measured by tide gauges indicates that 20th century sea level trends along the u s atlantic coast were not dominated by the characteristic spatial fingerprint of melting of the greenland ice sheet

intertidal foraminifera and stable isotope geochemistry from world s largest mangrove sundarbans assessing a multiproxy approach for studying changes in sea level abstract recent changes in sea level have appeared as a major threat to the existence of coastal habitats like mangroves and to the biodiversity characterizing such habitats in this study benthic foraminifer analysis along with carbon isotopes 13c and ratio between organic carbon and nitrogen c n were analyzed from five intertidal stations in sundarbans the world s largest mangrove ecosystem to test the efficiency of these signatures toward tracking relative rise in sea level the stability of these signatures with respect to gap of twenty months across varying elevations of the targeted stations has been tested benthic foraminifer abundance ranged from 0 to 118 individuals per 10 g and the assemblage was found to be mostly dominated by agglutinated species the 13c values 26 6 to 23 8 reflected that the origin of carbon is majorly from vascular land plants in some inputs from estuarine phytoplankton that are known to characterize tidal water of sundarbans the values of c n 0 48 1 43 represented a microbially degraded total organic carbon toc pool and thus were not a suitable proxy out of three signatures 13c showed a strong co relation with elevation and thus could be used as a reliable proxy to track relative sea level rise in mangrove environments

diagenesis of organic matter in georgia salt marshes abstract organic matter preserved in sediments of georgia salt marshes derives from spartina alterniflora and planktonic and bacterial substances sources and diagenesis of sedimentary organic material were studied by means of stable c and n isotopes and gas chromatography of pyrolysates from plants suspended sediments and a series of muds modern to 1400 years old from st catherines island georgia suspended particulate matter 20 m has isotopic compositions 13 c 18 to 22 which are composed of an average 34 42 plankton carbon and 58 65 higher plant detritus as determined by isotopic mass balance of the system the 13 c of bulk sediments and humic acids 13 c 18 to 19 extracted from them remain relatively constant over time the 13 c of acid hydrolysates however changed from 15 in surface marsh sediment to a 13 c of 19 from sediment sampled at a depth of 125 cm higher plant normal hydrocarbons are present in muds and in particulate matter from the water column and 13 c in lipids and gas chromatography of pyrolysates of samples reflect this addition with increasing age 15 n of total sediments and acid hydrolysates increases and the ratio of odd to even hydrocarbons in the pyrolysates decreases initially low density material in sediments consists primarily of plant fragments with time this material is decayed and diluted by microbial material changes that are reflected by more negative 13 c of 15 to 17 5 as compared to 13 c of 12 for moden spartina and the addition of n alkanes in the range of c 13 19 the isotopic heterogeneity in surface sediments with carbon as an example ranged from a 13 c of 15 plant fragments to 22 sediment following lipid humic acid and plant fragment extraction nowhere was the c isotopic composition of total spartina expressed even though microscopic plant pieces lignocellulose pyrolysis fragments and n alkanes from c 22 27 were detected in suspended particulate matter total sediments and humic acids

relationships between hydraulic variables and bedload transport in a subalpine channel colorado rocky mountains u s a abstract this study used three cross sections along a subalpine channel to examine associations between flow and sand and gravel bedload transport in a cobble bed channel at each section velocity was measured at 0 2 0 4 0 6 and 0 8 of flow depth for ten increments across the section at each increment velocity measurements were immediately followed by 10 min bedload samples with a 7 6 cm helley smith sampler linear regressions between bedload and flow variables suggest that grain shear stress stream power near bed velocity average velocity and the froude number are the most relevant indicators of bedload transport particularly when regressed against the d max or d 84 of the bedload grain size distribution no significant relationships however were constant at all three cross sections inconsistency in relationships between bedload discharge and hydraulic variables is at least in part the result of the extreme temporal and spatial variability present in east st louis creek photographs and observations made throughout the field season suggest the importance of random events such as tree fall and log jam formation in regulating bedload discharge the data from east st louis creek suggest equal mobility for sand and gravel transport

the morphologic structure of step pools in mountain streams abstract step pool sequences in streams in the santa monica mountains of southern california impart a characteristic morphologic structure that varies with slope but despite the strong association with slope that suggests a direct process control analysis of 464 step pools in 13 study reaches reveals the relationship to reflect correlation but not necessarily causality the direct control on step height is particle size whereas discharge is the probable causal process determining step wavelength because both particle size and discharge generally change with channel slope downstream a slope variation with step wavelength and height is the apparent indirect geometric result a conceptual model of process form linkages is proposed based on these results whereby the step pool morphology is produced by positive relationships between wavelength and discharge and between height and particle size the model offers new insights for explaining the step pool morphology and it is potentially useful in channeling future efforts toward the appropriate scales and variables

holocene sea level database from the atlantic coast of europe abstract high quality relative sea level rsl data reveal spatial and temporal variations in crustal movements during the holocene which are used for many applications ranging from calibrating models of earth rheology and ice sheet reconstructions to the development of coastal lowlands and human occupation here we present a holocene rsl database for the atlantic coast of europe ace and estimate rates of rsl change from the ace database using a spatio temporal empirical hierarchical model the database contains 214 index points which locate the rsl position in space and time and 126 limiting dates which constrain rsl to above or below a certain elevation at a specific point in time the temporal distribution extends from present to 11 5 ka with only 42 index points older than 7 ka the spatial distribution spans 1700 km from french flanders france to algarve portugal with more than half of the index points concentrated along the french coast the ace database shows rsl was below present during the holocene rates of rsl change were highest during the early holocene ranging between 6 8 0 5 mm yr 1 in middle portugal and 6 3 0 8 mm yr 1 in southern france from 10 to 7 ka mid to late holocene rates decreased over time with rates ranging between 0 9 0 4 mm yr 1 in middle france and 0 1 0 5 mm yr 1 in middle portugal from 4 ka to present comparison of the rsl data to output from a glacial isostatic adjustment model suggests that deglaciation of the british irish and fennoscandian ice sheets dominates the large scale variability captured by the ace database which reflects a decreasing influence of the collapsing british irish and fennoscandian peripheral forebulge that migrated from the northeast to the northwest after 4 ka

flandrian sea level changes in the fenland ii tendencies of sea level movement altitudinal changes and local and regional factors stratigraphic micropalaeontologic and radiocarbon data show that since c 6500 bp the fenland has been influenced by 7 periods of positive sea level tendencies and by 6 periods of negative sea level tendencies despite the numerous problems associated with the reconstruction of past altitudes of sea level the periods of positive sea level tendencies were clearly characterised by a rise in sea level the development of transgressive overlaps and a landward movement of the coastline the periods of negative sea level tendencies were characterised by the development of regressive overlaps a seaward movement of the coastline and a reduced or negative rate of sea level rise the various altitudinal errors do not permit the incontrovertible distinction of periods of falling sea levels all changes within the fenland were not synchronous and local factors influenced the exact nature of each sea level indicator dominant regional and local factors have been identified for different areas and different time periods the chronological and spatial characteristics of the sequences within the fenland are best explained by a palaeocoastline without supratidal barriers controlling sedimentation the data indicate an average crustal subsidence in the fenland of 0 9m 1000 years since c 6500 bp and the pattern of positive and negative tendencies of sea level movement is also seen in the chronologies for north west england and north east scotland

geometric scaling of step pools in mountain streams observations and implications understanding the geometric structuring of alluvial step pools is an enduring problem in mountain stream geomorphology many previous studies propose that the key control parameter governing the step pool form is mean bed slope as explored through several examples however we find that slope control formulations are inconsistently demonstrated for broad data sets on this basis we reexamine the bed form architecture of step pools with a new descriptive parameter termed the aspect ratio active stream width divided by step drop height we test with data collected from three different mountain settings for step pools observed over mean bed slopes ranging from 2 to 22 we find that step wavelength and height are well described by when these dimensions are normalized by the step drop height furthermore we observe that varies inversely with mean bed slope context for our findings is provided by recent field and laboratory work which highlights that the cross stream component to the overall flow structure in step pools and scour pools is significant this is important because it expands upon and relates our work to formative models which are based on jet scour and the associated three dimensional flow structure of step pools our work has practical implications for the design of step pool channels because existing approaches are based in large part on structuring artificial systems according to a narrowly defined geometry we observe however that under certain conditions this approach may yield constructed step pools that are unstable as an alternative approach we propose that the geometric relationships developed here can be applied to identify artificial step pool geometries that will be more fully reflective of natural analogs and thus possibly more stable

palaeoecological and possible evolutionary effects of early namurian serpukhovian carboniferous glacioeustatic cyclicity early namurian serpukhovian carboniferous sedimentary cycles in the throckley and rowlands gill boreholes near newcastle upon tyne uk consist of fossiliferous limestones overlain by usually unfossiliferous black mudstone followed by sandstones and often by thin coal seams sedimentological and regional geological evidence suggests that the largest are high amplitude cycles probably of glacioeustatic origin 13 c bulk organic matter delineates marine and non marine conditions because of the large difference between terrestrial and marine 13 c and indicates that full marine salinity was only intermittent and resulted from glacioeustatic marine transgression superimposed on a background of inundation by freshwater from large rivers which killed off the marine biota palynology suggests that plant groups including ferns and putative pteridosperms were affected by changing sea level and that there is a theoretical possibility of connection between cyclicity and the first appearance of walchiacean conifer like monosaccate pollen such as potonieisporites long term terrestrial and marine increasing 13 c organic may reflect the onset of major glaciation in gondwana as there is evidence to suggest that the two are coeval but no specific mechanism can be suggested to link the trends

holocene sea level database for the atlantic coast of the united states we have constructed a database of holocene relative sea level rsl observations for the atlantic coast of the united states the database contains 492 index points which locate the position of rsl in time and space and 344 limiting dates which constrain the minimum or maximum limit of former sea level the majority of the index points in the database are from 6 ka bp to present with only 7 older than 6 ka bp spatially index points are distributed between maine and south carolina but there is an absence of data from georgia and the atlantic coast of florida the database is sub divided into 16 regions based on the distance from the former laurentide ice sheet and are classified depending upon their susceptibility to compaction the index points and limiting data demonstrate that rsl did not exceed present 0 m during the holocene except potentially in regions 1 and 2 eastern maine and southern maine rates of rsl change were highest during the early holocene and have decreased over time due to the diminishing response of the earth s mantle to glacial isostatic adjustment and reduction of ice equivalent meltwater input along the atlantic coast of the united states the linear rate of rsl rise prior to 4 ka bp ranged from 0 5 to 4 5 mm a 1 compared to 0 6 1 8 mm a 1 from 4 ka bp to ad 1900 the database suggests minimal 0 3 mm yr changes in these rates of rsl rise during the late holocene deglaciation of the laurentide ice sheet caused the spatial variability captured by the database the maximum rate of late holocene and ongoing rsl rise occurred in mid atlantic regions new jersey and inner delaware because of collapse of the peripheral forebulge

stream bed stabilization using boulder check dams that mimic step pool morphology features in northern italy during the last 10 years the check dams made of boulders have been fully employed for torrent management particularly for high gradient stream stabilization the analysis of this typology is shown in relation to three aspects building features field of use and design according to geomorphologic principles the maso di spinelle torrent located in the province of trento italy north italian alps is an example where a sequence of low check dams made of boulders have been used for bed stabilization the design criteria are taken from the step pool morphology features and the results are encouraging for further applications the artificial step pool grade control structures in the maso di spinelle torrent have been successfully tested by floods events with return periods of about 7 10 and 20 25 years

micropaleontologic record of late pliocene and quaternary paleoenvironments in the northern albemarle embayment north carolina u s a abstract micropaleontological data provide a strong actualistic basis for detailed interpretations of quaternary paleoenvironmental change the 90 m thick quaternary record of the albemarle embayment in the mid atlantic coastal plain of the usa provides an excellent opportunity to use such an approach in a region where the details of quaternary environmental change are poorly known the foraminiferal record in nine cores from the northern outer banks east of albemarle sound north carolina indicates the deposition of subhorizontal mostly open marine early to late pleistocene units unconformably upon a basement of late pliocene reduced oxygen fine grained shelf basin deposits pollen data record several warm cool fluctuations within the early to mid pleistocene deposits diatom data indicate that some fresh and brackish water units occur within the generally open marine pleistocene succession a channel cut by the paleo roanoke river during the last glacial sea level lowstand occurs in the northern part of the study area pollen indicates that the basal fluvial valley fill accumulated in cooler than modern climate conditions in the latest pleistocene overlying silts and muds accumulated under cool climatic estuarine conditions according to diatom and pollen data radiocarbon ages from the estuarine deposits indicate that the bulk of these sediments accumulated during the latest pleistocene the estuarine channel fill deposits are overlain by holocene open marine sands deposited as the rising sea transgressed into the estuary approximately 8 5 to 9 0 kyr bp within the barrier island drill cores of this study fully marine sedimentation occurred throughout the holocene however immediately west of the present barrier island mid to late holocene estuarine deposits underlie the modern albemarle sound the islands that currently form a continuous barrier across the mouth of albemarle sound have a complex history of holocene construction and destruction and large portions of them may be less than 3 kyr old the barrier island sands overlie open marine sands of colington shoal in the north and to the south overlie fluvial and marine sand filling paleo roanoke tributary valleys the pleistocene sediments underlying the northern outer banks study area are mainly of open inner to mid shelf origin if as is likely sea level continues to rise a return to such environmental conditions is likely in the near future

controls on large boulder mobility in an auto naturalized constructed step pool river san clemente reroute and dam removal project carmel river california usa

signatures of tetraether lipids reveal anthropogenic overprinting of natural organic matter in sediments of the thames estuary uk intertidal foreshore sediments from a 110 km stretch of the thames estuary were analysed for glycerol dialkyl glycerol tetraethers gdgts to track soil organic matter om input and evaluate the impact of coastal urbanisation on their distribution concentration of branched br gdgts ranged from 1 to 15 g g organic carbon oc and crenarchaeol ranged from 0 6 to 19 g g oc an overall decrease in brgdgts was observed from the inner thames brentford to the outer thames isle of grain suggesting a drop in soil om input towards the sea in contrast crenarchaeol concentration was highest around east london rather than towards the open sea such elevated crenarchaeol concentration occurred in the section of the river most influenced by anthropogenic pollution such as discharge points for london s major sewage treatment plants docks and power plants the non systematic spatial distribution of crenarchaeol was also reflected in the branched isoprenoid tetraether bit index the highest bit values occurred upstream and in close proximity to salt marshes 0 8 1 whereas the lowest values 0 3 0 5 were towards the sea however unusually low values 0 4 were observed in the river section that had high crenarchaeol concentration in contrast bulk 13c values were insensitive to london s anthropogenic influence this suggests that the natural systematic decrease in bit index in the estuary is overprinted by london s anthropogenic activity between deptford creek and tilbury we therefore advise caution when interpreting the bit index for sediments in close proximity to megacities discharging industrial and municipal waste that can become incorporated into the near surface sedimentary record

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

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

proxy records of holocene storm events in coastal barrier systems storm wave induced markers abstract extreme storm events in the coastal zone are one of the main forcing agents of short term coastal system behavior as such storms represent a major threat to human activities concentrated along the coasts worldwide in order to better understand the frequency of extreme events like storms climate science must rely on longer time records than the century scale records of instrumental weather data proxy records of storm wave or storm wind induced activity in coastal barrier systems deposits have been widely used worldwide in recent years to document past storm events during the last millennia this review provides a detailed state of the art compilation of the proxies available from coastal barrier systems to reconstruct holocene storm chronologies paleotempestology the present paper aims i to describe the erosional and depositional processes caused by storm wave action in barrier and back barrier systems i e beach ridges storm scarps and washover deposits ii to understand how storm records can be extracted from barrier and back barrier sedimentary bodies using stratigraphical sedimentological micro paleontological and geochemical proxies and iii to show how to obtain chronological control on past storm events recorded in the sedimentary successions the challenges that paleotempestology studies still face in the reconstruction of representative and reliable storm chronologies using these various proxies are discussed and future research prospects are outlined

using foraminiferal transfer functions to produce high resolution sea level records from salt marsh deposits maine usa quantitative analyses of foraminiferal distributions along the coast of maine are used to provide transfer functions for reconstruction of sea level changes from fossil foraminiferal assemblages the indicative meaning of fossil assemblages is most accurately predicted by a training set that incorporates live and dead foraminifera and that uses flooding duration not height as the predictor variable sea level records are produced for two sites in maine usa a middle marsh site in scarboro and a high marsh site in machiasport these records offer temporal resolution of five to seven years and span the past century they are compared with instrumental data from a nearby tidal station to assess their accuracy strong correlations are found between the geologic records and the observational data in particular between the foraminiferal record from machiasport and the tide gauge record from eastport r2 0 83 p 0 005 thus a foraminifera based transfer function approach offers great potential for reso