hydrogeomorphic influences on salt marsh sediment accumulation and accretion in two estuaries of the u s mid atlantic coast abstract salt marshes in two contrasting estuaries of the u s mid atlantic coast barnegat bay and delaware bay were investigated to identify relationships between rates of sedimentation and marsh estuarine geomorphic setting barnegat bay is a microtidal lagoon estuary with back barrier and mainland coastal marshes whereas delaware bay is a micro mesotidal coastal plain estuary with sediment rich estuarine marshes salt marshes of both estuaries are dominated by spartina alterniflora an analysis was performed to characterize marsh hypsometry and tidal flooding characteristics and a coring study was conducted to measure rates of mineral sediment accumulation organic matter accumulation and vertical accretion using 137 cs and 210 pb chronology at nine sites in both estuaries mineral sediment and organic matter accumulation rates were significantly higher in delaware bay marshes sediment mean and 1 2 57 2 03 kg m 2 year 1 organic 0 65 0 26 kg m 2 year 1 than in barnegat bay sediment 0 31 0 27 kg m 2 year 1 organic 0 29 0 08 kg m 2 year 1 as were rates of accretion delaware bay 0 79 0 06 cm year 1 barnegat bay 0 28 0 06 cm year 1 regression analysis indicated that marsh accretion rates were positively correlated with rates of sediment and organic accumulation but the upper limit of accretion was governed by sediment accumulation tidal flooding frequency and duration did not correlate with marsh accumulation or accretion rates in either estuary suggesting that hydroperiod is subordinate to sediment availability in governing rates on 50 100 year time scales if true natural and or human influences on suspended sediment production and transport in these estuaries has potential to impact marsh accretionary status and stability independent of sea level rise

holocene evolution of an estuarine coast and tidal wetlands modern facies distribution patterns extensive core data and chronostratigraphic cross sections provide a detailed history of holocene inundation within the delaware bay estuary and sedimentation in adjacent coastal environments flooding of the estuary occurred with rising sea level as the shoreline retreated northwest along a path determined by the pre transgression topography simultaneous migration of an estuarine turbidity maximum depocenter provided the bulk of fine sediments which form the coastal holocene section of the estuary prior to 10 ka the ancestral bay was predominantly a tidal river and the turbidity maximum depocenter was located southeast of the modern bay mouth by 10 ka lowlands adjacent to the ancestral channel of the delaware river were flooded forming localized tidal wetlands and the depocenter had initiated high rates of fine grained sedimentation near the present bay mouth at that time coastal holocene strata began to onlap the interfluve highlands by 8 ka the fine grained depocenter had migrated northwest along the main channel of the delaware river although the widened mouths of tributary valleys continued to be active sites of sediment accumulation following the passage of the fine grained depocenter coarse grained sediments accumulated along the coast in response to increased wind wave activity during the middle holocene portions of the estuarine coast began to resemble modern geomorphology and washover barrier sands and headland beach sandy gravels accumulated along the southwest shore the late holocene was characterized by erosional truncation and submergence of aggraded coastal lithofacies and by planation of remnant highland areas knowledge of the eroded holocene section is fragmentary at present continued sea level rise is accompanied by deposition of tidally transported muds in coastal environments and deposition of sandy sediments in some offshore regions an unconformity marks the base of the developing open estuarine sequence of coarse clastic lithofacies and denotes the end of coastal accumulations modeling of coastal lithofacies transitions identifies specific lithofacies complexes in the holocene stratigraphic section which were influential in the evolution of the coast development of the holocene section of the estuary coast involved both constructive or aggradational and destructive or erosional phases

molybdenum behavior during early diagenesis insights from mo isotopes 1 we present molybdenum isotope and concentration data from 14 sites in the eastern pacific from the central california to the peru margin the environments studied have been chosen to represent a broad range in oxidation reduction redox potential which provide a framework for the behavior of this redox sensitive element manganese rich hemipelagic sediments from the eastern tropical pacific have a mean characteristic mo isotope signature 98 95mo 0 49 0 04 two times the standard deviation of the mean 2 sdom with n 14 that reflects fractionation between ocean water and authigenic mo associated with mn oxides authigenic fe mo s deposits from reducing continental margin settings also have a characteristic mo isotopic signature 98 95mo 1 64 0 04 2 sdom with n 136 both of these values are in contrast to highly sulfidic 11 m h2saq restricted basin environments which contain mo isotope values analytically indistinguishable from seawater in terms of the mo isotope composition the modern oceanic mo sink is dominated by continental margin type environments where 98 95mo 1 6 and mn rich sediments where 98 95mo approximately 0 5 with a minor contribution from euxinic settings where h2saq 11 m

holocene depocenter migration and sediment accumulation in delaware bay a submerging marginal marine sedimentary basin abstract the holocene transgression of the delaware bay estuary and adjacent atlantic coast results from the combined effect of regional crustal subsidence and eustasy together the estuary and ocean coast constitute a small sedimentary basin whose principal depocenter has migrated with the transgression a millenial time series of isopach and paleogeographic reconstructions for the migrating depocenter outlines the basin wide pattern of sediment distribution and accumulation upland sediments entering the basin through the estuarine turbidity maximum accumulate in tidal wetland or open water sedimentary environments wind wave activity at the edge of the tidal wetlands erodes the aggraded holocene section and builds migrating washover barriers along the atlantic and estuary coasts of delaware the area of the upland environment decreases from 2 0 billion m 2 to 730 million m 2 during the transgression the area of the tidal wetland environment increases from 140 million to 270 million m 2 and due to the widening of the estuary the area of open water increases from 190 million to 1 21 billion m 2 gross uncorrected rates of sediment accumulation for the tidal wetlands decrease from 0 64 mm yr at 6 ka to 0 48 mm yr at 1 ka in the open water environments uncorrected rates decrease from 0 50 mm yr to 0 04 mm yr over the same period we also present data on total sediment volumes within the tidal wetland and open water environments at specific intervals during the holocene

late wisconsinan holocene paleogeography of delaware bay a large coastal plain estuary abstract analyses of an extensive grid of seismic reflection profiles along with previously published core data and modern sedimentary environment information from surrounding coastal areas permit an outline of the paleogeography of the large delaware bay estuary during the last transgression of sea level during late wisconsinan times the delaware river system eroded a dendritic drainage pattern into the gravelly and muddy sands of tertiary and younger age beneath the southern half of the lower bay area this system included the trunk valley of the ancestral river and a large tributary valley formed by the convergence of secondary streams along the delaware coast the evolution of the estuary from this drainage system proceeded as follows 1 when local relative sea level was at 50 m the head of the tide reached the present bay mouth area 2 at 40 m possibly 15 000 12 000 yrs ago the trunk valley of the drainage system was a tidal river that extended more than 30 km up the bay and a small contiguous inlet existed at the bay mouth 3 at 30 m approximately 11 000 10 000 yrs ago the estuary comprised two narrow passages formed by the drowning of the main and tributary river valleys and the bay mouth inlet was 5 6 km wide 4 at 20 m between 8000 and 7000 yrs ago the two passages of the estuary were joined except for a series of small islands on top of a low intervening ridge and the inlet channel was 11 km wide 5 at 10 m between 6000 and 5000 yrs ago the estuary was nearly continuous and encompassed about 60 of the present lower bay area thin coarse grained fluvial deposits accumulated initially within the main channels of the former drainage system as base level was elevated by rising sea level during the subsequent development of the estuary clayey silts were deposited rapidly beneath the nontidal estuarine depocenter turbidity maximum as it migrated through the bay area and organic muds accumulated in tidal wetlands that occupied the mouths of tributaries and small marginal embayments as the fetch and tidal prism of the estuary increased narrow barrier and headland beaches composed of fine to coarse sands were formed locally along the bay shorelines in the later stages of development sediment scour reworking and transport became the dominant processes within the open estuary data from this study demonstrate the great temporal and spatial variability of sedimentary deposits within large drowned river valley estuaries and outline a model that can be used to interpret ancient estuarine strata

estuarine channel evolution in response to closure of secondary basins an observational and morphodynamic modeling study of the western scheldt estuary the fringes of estuaries are often characterized by the presence of side embayments secondary basins with dimensions in the order of hundreds of meters to tens of kilometers the presence of secondary basins significantly alters the hydrodynamic and sediment characteristics in the main estuary implying that loss of secondary basin area due to human interventions might affect the estuarine morphodynamics analysis of historical bathymetric data of the western scheldt estuary netherlands suggests that closure of its secondary basins has triggered the observed lateral displacement of the nearby channels this analysis motivated investigation of the impact of secondary basins on decadal evolution of estuarine channels using the numerical model delft3d model results show that channels that form near a secondary basin are located farther away from the bank of the estuary with respect to their positions in the case without a basin overall results in cases with two or three basins are similar to those in case with one single basin the wider the basin the farther away the nearby channel forms removing a secondary basin causes a lateral displacement of the nearby channel toward the bank indicating that the observed lateral displacement of channels in the western scheldt is triggered by closure of its secondary basins the physical explanation is that tidal currents in the main estuary are weaker and more rotary near secondary basins favoring sediment deposition and shoal development at these locations model results are particularly relevant for estuaries with moderate to high friction and converging width

understanding fine grained river sediment dispersal on continental margins studies of fine grained sediment dispersal in the marine environment have documented diversity in the behavior of depositional systems on continental margins with different oceanographic conditions and morphologies based on the pattern and nature of sediment accumulation for twenty three case studies we propose there are five basic types of dispersal systems and these are related to river wave tide and margin characteristics data suggest that the type of dispersal system on any margin can be predicted with knowledge of sediment load mean significant wave height tidal range and continental shelf width at a river mouth and from these a hierarchical decision tree is developed analysis of the dispersal system type of more than 100 river mouths reveals that proximal accumulation dominated pad and marine dispersal dominated mdd systems are most abundant but estuarine accumulation dominated ead systems also are anticipated to be numerous globally research quantifying marine sediment dynamics in these system types is needed although less common the size and nature of subaqueous delta clinoform sdc and canyon captured cc systems also warrant future attention to their study strong correlations between physical characteristics i e significant wave height and tidal range and the depth and distance to the nearest maximum shelf depocenter provide evidence that in reality a continuum exists between the system types the process related partitioning of sediment in the five different types of marine dispersal systems has important implications for understanding the stratigraphic record and the cycling of carbon

holocene sea level history and neotectonics of the united states mid atlantic region applications and corrections published local relative holocene sea level histories derived from various dated materials at positions along the united states east coast fail to agree on the timing and magnitude of sea level change published eustatic curves suffer the same disagreement and have lead to recent declarations in the literature that a true eustatic history is unattainable this has been generally accepted by workers in light of the myriad of complicating factors which have been identified as influencing the position of sea level through time in this study a single local relative sea level curve kraft 1976 has been analyzed for elevation and temporal errors resulting from fine sediment compaction paleotidal range and neotectonic phenomena additionally the cross latitude history of vertical crustal velocity along the united states east coast is suggested as providing a means of correlating adjacent curves which have been corrected in such a manner this enhances the applicability of a local relative curve for purpo

comparisons of 210pb and pollen methods for determining rates of estuarine sediment accumulation abstract comparisons of sedimentation rates obtained by 210 pb and pollen analyses of 1 m cores collected throughout the potomac estuary show good agreement in the majority of cores that can be analyzed by both methods most of the discrepancy between the methods can be explained by the analytical precision of the 210 pb method and by the exactness with which time horizons can be identified and dated for the pollen method x radiographs of the cores and the distinctness of the pollen horizons preclude significant displacement by reworking and or mixing of sediments differences between the methods are greatest where uncertainties exist in assigning a rate by one or both methods i e 210 pb trends and or possible horizon assignments both methods show the same relative rates with greater sediment accumulation more common in the upper and middle estuary and less toward the mouth the results indicate that geochronologic studies of estuarine sediments should be preceded by careful observation of sedimentary structures preferably by x radiography to evaluate the extent of mixing of the sediments time horizons whether paleontologic or isotopic are generally blurred where mixing has occurred precluding precise identification whenever possible two methods should be used for dating sediments because a rate albeit erroneous can be obtained isotopically in sediments that are mixed accurate sedimentation rates are also difficult to determine where the time boundary is a zone rather than a horizon where the historical record does not provide a precise date for the pollen horizon or where scouring has removed some of the sediment above a dated pollen horizon

long term accretion rates on tidal salt marshes abstract long term variations in salt marsh accretion rates were estimated using data collected on the marshes of the north norfolk coast england fourteen discrete marsh areas were sampled all lying within a 20 km stretch of coast the age of each marsh had previously been determined using radiocarbon or archival evidence for the date of vegetation inception on each marsh surface marsh ages ranged from 10 years to 2000 years the elevation of each marsh surface was determined in the field using levelling techniques the relationship between age and surface elevation was assumed to be a function of the rate of marsh accretion within this area of coast statistical tests showed this to be a highly significant relationship while the accretion rates calculated from the age height curve agree closely with field measurements on these marshes accretion rates were found to vary from 1 7 cm yr on 10 year old marshes to less than 0 002 cm on marshes older than 500 years the age height relationship describes an asymptotic curve with the asymptote lying 0 8 m below the level of the highest spring tides and appears to be controlled by the frequency of tidal maxima which peaks at 0 8 m below the maximum value and declines sharply above that height

quaternary fluvial history of the delaware river new jersey and pennsylvania usa the effects of glaciation glacioisostasy and eustasy on a proglacial river system abstract fluvial glacial and estuarine deposits in the delaware valley record the response of the delaware river to glaciation sea level change and glacioisostasy during the quaternary incision following an early pleistocene glaciation created the present valley which is inset into a pliocene strath and fluvial plain middle and upper pleistocene and holocene deposits were laid down in this inset valley estuarine terraces in the lower valley and bayshore at 20 m probably marine isotope stage mis 11 8 m mis 5e and 3 m mis 5a or c and a fluvial deposit that correlates to offshore mis 3 marine deposits at 20 m are at elevations consistent with glacioisostatic models successive incisions during lowstands in the middle and late pleistocene lengthened deepened and narrowed the channel in the lower valley and shifted the channel westward in delaware bay during mis 2 glaciation from 25 to 18 ka the delaware was diverted to the hudson shelf valley by glacioisostatic tilting most glacial sediment was trapped in fluvial lacustrine valley fills north of the terminal moraine incision of the valley fill was accomplished during the early stage of rebound between 17 and 12 ka drainage to the delaware shelf was restored between 15 and 13 ka as the forebulge collapsed during incision multiple postglacial terraces formed where the valley was perpendicular to rebound contours and so was steepened and elevated northward and a single terrace formed where the valley paralleled the contours and there was no differential elevation or steepening about 65 of the original volume of mis 2 glacial sediment remains in the main valley and most of the eroded volume is in the channel in the lower valley beneath holocene estuarine fill little glacial sediment reached the delaware or hudson shelf overbank deposition on the lower postglacial terrace and modern floodplain spans the holocene the volume of holocene sediment in the estuary and bay yields a basinwide denudation rate of about 20 m my

late stage estuary infilling controlled by limited accommodation space in the hudson river high resolution seismic data and sediment cores reveal the late holocene subsurface stratigraphy of the broad tappan zee piermont region of the hudson river estuary we identify a series of distinct extensive horizons beneath the marginal flats channel banks and main channel in this area physical properties and lithology from sediment cores suggest that these horizons are surfaces of erosion or nondeposition radiocarbon dates indicate that they correspond with three distinct time horizons with maximum ages of 3400 2200 and 1600 yr bp we also distinguish two sedimentary facies that occupy the marginal flats and channel banks the deeper facies forms a deposit 2 km wide and 7 km long that accumulated at rates of 2 4 mm yr in the vicinity of the sparkill creek prior to 1700 yr bp overlying and onlapping the 2200 yr bp seismic surface based on its internal geometry morphology and proximity to a tributary we interpret this facies as a delta deposit the shallower facies accumulated more slowly 1 2 mm yr overlying the delta deposit to the south and dominating the marginal flats to the north surface sediment samples and geophysical data reveal that the modern marginal flats are no longer actively depositional but dominated by nondeposition or erosion limited accommodation space in the hudson river estuary may be the critical factor contributing to the observed sedimentary pattern characterized by intervals of deposition punctuated by episodes of erosion an estuarine system that has reached a state of morphological equilibrium will be sensitive to even small fluctuations in sea level and climate conditions which may account for the intervals of deposition and erosion we observe limited accommodation space and intermittent sediment deposition in the hudson river estuary may be due to its evolution from a fjord filled with glacial lake sediments which distinguishes its infilling behavior from the classic drowned river valley estuary

towards balancing the oceanic ni budget abstract nickel isotopes are a novel and promising tracer of the chemistry of past ocean environments but realisation of this tracer s potential requires a comprehensive understanding of the controls on ni burial in the marine sedimentary archive an outstanding puzzle in the marine budget of ni first recognised in the 1970s is a major imbalance in the known inputs and outputs to and from the ocean the sedimentary outputs of ni are much larger than the inputs rivers dust much more recently it has also been recognised that the outputs are also considerably isotopically heavier than the inputs in this study we find light ni isotope compositions 60 ninist srm986 0 2 to 0 8 for mn rich sediments from the eastern pacific compared to fe mn crusts at about 1 6 these data suggest that diagenetic remobilisation of isotopically heavy ni leads to a significant benthic ni flux estimated at 0 6 2 3 10 8 mol yr similar in magnitude to the riverine flux to the ocean diagenetic remobilisation of ni may occur either via cycles of mn oxide dissolution and precipitation with associated ni sorption and release or during mineralogical transformation of birnessite to todorokite a minor role for retention of isotopically light ni by fe oxides or fe rich authigenic clays is also proposed overall a benthic flux of isotopically heavy ni at about 3 can balance the marine ni budget pinpointing diagenesis as a key missing piece of the ni puzzle

tidal wetland record of holocene sea level movements and climate history abstract paleontological geochemical and lithological indicators of former marine and nonmarine influence are correlated between 13 cores from a tidal wetland wolfe glade on the southeast coast of delaware bay twenty new radiocarbon dates are used to establish the chronostratigraphy of marsh facies sediment iron content weight loss on ignition and remains of plants diatoms and foraminifera known to tolerate specific tidal inundation cycles are used to describe cored facies originating from supratidal intertidal and subtidal salt marsh subenvironments pollen assemblages are used to infer local holocene climate fluctuations and to reconstruct paleoenvironments during marsh evolution the record of paleoclimatology suggests the atlantic chron was warm with variable humidity in the region whereas the subboreal was dominated by cool and humid conditions the subatlantic was warmer and initially dryer with a cool humid phase prior to about 1 ka returning to warmer humid conditions in the last several centuries local relative sea level movements are characterized by five rapid short term episodes when the rate of sea level rise accelerated relative to the rate of marsh aggradation these episodes are recorded by transgressive facies contacts at 5 3 0 2 ka 4 4 0 2 ka 3 25 0 2 ka and 1 8 0 2 ka sidereal years an earlier transgressive facies contact dated 6 9 0 2 ka is probably not the product of a true sea level movement sea level movements are recorded throughout the marsh as palustrine or high marsh peats or peaty overlain by lower intertidal or subtidal marine deposits several features suggest that these episodes are local relative transgressions produced by short term accelerations in the rate of sea level rise relative to marsh aggradation the contemporaneity and apparent suddenness of marine inundations the sequence of facies indicating marine drowning the presence of similar events in marshes elsewhere in delaware bay and the marsh wide extent of indicative facies transitions we propose that the rapid and frequent sea level movements observed in wolfe glade are the result of surges and relaxations in the gulf stream and associated spin up and partial collapse of the north atlantic gyre in response to winds generated by changes in the north atlantic atmospheric thermal gradient associated with holocene climate fluctuations

sequential leaching of marine ferromanganese precipitates genetic implications abstract sequential leaching experiments were carried out on twenty one hydrogenetic crust samples from different locations in the central pacific and the results are compared with four crust and nodule samples of different genetic origin fe vernadite mno2 is the most important minor and trace metal bearing mineral phase and shows high concentrations of co ni cd ti ba zn and cu which are present in seawater mainly as hydrated and labile complexed cations elements forming carbonate and hydroxide complexes and oxyanions in seawater like pb mo v and minor proportions of cu and zn are bound in the fe00h fraction the ca carbonate phase and the residual fraction which consists of aluminosilicates and crystalline oxides show only minor heavy metal associations e g cu and zn only a small part of the high ti concentrations in hydrogenetic crusts is of detrital origin ti mainly forms a hydrogenetic phase probably consisting of ti02 2h20 intergrown with the amorphous fe00h phase analyses of different sample types and crust layers show that aging and diagenetic effects can change the phase associations of some elements the most notable change was observed for pb which during phosphatization of crusts is transferred from the mn fe oxide fraction to the apatite fraction a colloid chemical model for the hydrogenetic precipitation of ferromanganese crusts on seamounts is proposed in the first stage mn2 rich water from the oxygen minimum zone is mixed with oxygen rich deep water and oxidized mn iv and other metals like fe ti al and si form oxide and hydroxide colloids these form mixed colloidal phases and scavenge trace metals by sorptive processes which are dominated by coulombic and chemical interactions between colloid surfaces and dissolved metal species in stage two the colloidal phases precipitate on the substrate rocks of the seamounts as ferromanganese oxide encrustations incorporating the sorbed heavy metals into the mineral phases

epeirogenic plate movements consideration is given to the kinematics of epeirogenic movements over the recent geologic past late pleistocene in a region for which there is an abundance of geological and geophysical information the continental shelf off the east coast of north america it is found that there has been a relative change in elevation of 140 m downward toward the northeast over this longitudinal distance of 3000 km during the past 18 000 years specifically miami has been elevated at a rate of 0 8 cm yr with respect to the scotian shelf continental margin the confirming data include the shelf break corrected for progradation reef building and glacio isostatic adjustment late pleistocene shores on the continental shelf earlier pleistocene unconformity surfaces dated geologic samples of known shallow water origin buried pleistocene channels and recent leveling analysis

geologic and human factors in the decline of the tidal salt marsh lithosome the delaware estuary and atlantic coastal zone abstract two to three thousand years ago the fringing tidal salt marsh wetlands including brackish and freshwater marsh of the delaware coastal zone were three to four times wider than at present observed variations in rates of marsh surface aggradation suggest that some areas are undergoing inundation whereas many other areas are undergoing aggradation at rates greater than sea level rise as measured by a local tidal gauge average 33 cm century based on a 70 year record and may be undergoing floral succession accompanying these sedimentary processes are coastal erosion rates up to 6 9 m yr along the delaware estuary up to 2 8 m yr along the delaware atlantic coast and ranging from 0 1 m yr to 0 6 m yr along the delaware atlantic coastal lagoons human development has destroyed nearly 9 of delaware s fringing salt marshes between 1938 and 1975 the rapidly growing trend toward hardening the edge of the adjacent landward uplands leads us to the conclusion that much of the fringing salt marsh of delaware will disappear over the next two to three centuries with only small remnants declining to extinction ca 1500 1700 years into the future impacts on the state of delaware comprised of 13 fringing salt marshes 1 4 century ago will be profound in terms of destruction of a large segment of the atlantic coastal or eastern north american migratory bird flyway and an eventual forced accommodation of the inhabitants of delaware to these naturally ongoing geological processes

neotectonism along the atlantic passive continental margin a review abstract an extensive body of geologic data including the modern state of stress historical seismicity surface and subsurface stratigraphy numerical models of crustal deformation surficial geomorphic systems and historical precise leveling and tidal gauge records constrain the style and rate of neotectonic deformation for the appalachians and atlantic passive continental margin there are two major styles of neotectonism in the eastern united states the northeastern united states is dominated by isostatic uplift and northward migration of peripheral bulge collapse in response to deglaciation this locally rapid but decreasing rate of deformation is superimposed upon slower long term deformation along the atlantic margin most of the long term continental margin deformation is attributed to lithospheric flexuring in response to sediment loading in sedimentary basins especially the baltimore canyon trough and carolina trough isostatic deformation in response to continental denudation and water loading of the shelf and stress from far field plate tectonic sources significant deformational features include an uplift anomaly near cape fear n c northward and southward tilting of the coastal plain into the salisbury and southeast georgia embayments respectively seaward tilting of the coastal plain piedmont and a complex pattern of postglacial uplift and later subsidence in the northeast estimates of vertical crustal velocities for similar locations vary over several orders of magnitude measurement interval bias and systematic leveling errors may account for some of the discrepancies evidence for periodic deformation in the eastern united states in substantial and it is possible that historic data indicate a period of accelerated deformation along the atlantic continental margin

stable isotope compositions of sedimentary organic carbon in tampa bay florida u s a implications for evaluating oil contamination 13cpdb values for sedimentary organic carbon in tampa bay florida and adjacent riverine systems range from 28 up the rivers to 20 in the middle of the bay to 10 in several contiguous small bays along the gulf of mexico coastline these values reflect the compositions of the plant precursors that is c3 land plants phytoplankton and sea grasses respectively which predominate in each of these areas organic carbon percentages range from 5 0 to less than 0 1 with a moderately good correlation relative to the 63gm sediment grain size fraction 0 76for67samples in addition to providing another interesting scenario of 13c signatures that are useful in understanding the contemporary deposition of organic carbon on the one hand and ancient depositional environments on the other these data are also shown to be useful in assessing the contribution of oil residues to the sediments should an oil spill occur in tampa bay at some time in the future

the process of sedimentation on the surface of a salt marsh abstract an unditched salt marsh creek drainage basin holland glade marsh lewes delaware has a sedimentation rate of 0 5 cm year 1 during normal storm free conditions the creek carries negligible amounts of sand and coarse silt of the material in the waters flooding the marsh surface over 80 disappears from the floodwaters within 12 m of the creek about one half of the lost material is theoretically too fine to settle even if flow were not turbulent however sediment found on spartina stems can account for the loss the quantity of suspended sediment that does reach the back marsh during these normal tides is inadequate to maintain the marsh surface against local sea level rise this suspended sediment is also much finer than the deposited sediments additionally remote sections of low marsh sections flooded by only the highest spring tides have 15 30 cm of highly inorganic marsh muds this evidence indicates that normal tidal flooding does not produce sedimentation in holland glade study of the effects of two severe storms of a frequency of once per year suggests that such storms can deposit sufficient sediment to maintain the marsh the actual deposition of fine grained sediments fine silt and clay appears to result primarily from biological trapping rather than from settling in addition this study proposes that the total sedimentation on mature marshes results from a balance between tidal and storm sedimentation storms will control sediment supply and movement on micro and meso tidal marshes and will have less influence on macro tidal marshes

holocene environmental and parasequence development of the st jones estuary delaware usa foraminiferal proxies of natural climatic and anthropogenic change abstract the benthic foraminiferal record of marshes located along western delaware bay st jones estuary usa reflects the response of estuaries to sea level and paleoclimate change during the holocene system tracts are recognized and within them parasequences based on sedimentological and foraminiferal assemblages identification the parasequences defined by foraminiferal assemblages appear correlative with rapid holocene climate changes that are of worldwide significance 6000 5000 4200 3800 3500 2500 1200 1000 and 600 cal years bp following postglacial sea level rise modern subestuaries and marshes in the region began to develop between 6000 and 4000 years bp depending on their proximity to the mouth of delaware bay and coastal geomorphology initial sediments were fluvial in origin with freshwater marshes established around 4000 years bp the subsequent sea level transgression occurred sufficiently slowly that freshwater marshes alternated with salt marshes at the same sites to around 3000 years bp locally another two transgressions are identified at 1800 and 1000 years bp respectively marine influence increased in the estuaries until 600 years bp little ice age when regression occurred sea level began to rise again during the mid 19th century at the end of the little ice age when marshes became established the presence of a sand lens in the upper and middle estuary and the reduction in the number of tests in the top samples in cores from the same area also suggest an anthropogenic influence the estuary infill resulted in a sharp transgressive sequence represented by salt marsh foraminiferal assemblages in the upper part of the cores the increase in marsh foraminifera in both areas suggests an increase in marine influence that might be due to the transgression beginning at the end of the little ice age about 150 180 years ago coupled with anthropogenic straightening of the channel in 1913

late quaternary evolution of the upper reaches of the solent river southern england based upon marine geophysical evidence geological evidence suggests that during the late quaternary a river system the solent river drained a large part of central southern england its upper reaches flowed in a west east direction flanked to the south by a chalk ridge the purbeck isle of wight chalk ridge today only part of the upper reaches of the river9s tributary channels remain as the area was inundated during the flandrian transgression forming an embayment system poole and christchurch bays in order to map the offshore buried channels of the upper reaches of the solent river an extensive set of shallow marine geophysical data was analysed and interpreted the results of this investigation show that the solent river system was disrupted irreversibly by southerly capture of its upstream section before the flandrian transgression this disruption was the result of the fluvial breaching of the southern barrier of the system the purbeck isle of wight ridge at three points probably during late devensian time poole bay was first to be submerged during the transgression the estuaries which resulted from the drowning of the fluvial palaeovalleys of poole bay were infilled with transgressive facies sequences which have been preserved within the buried palaeovalleys in contrast christchurch bay was submerged at a later time but because of the abrupt manner of its inundation no transgressive facies have been preserved within its buried palaeovalleys

chemical and biological weathering of oil from the amoco cadiz spillage within the littoral zone the spillage of oil from the wreck of the supertanker amoco cadiz resulted in massive oiling of the littoral zone along 320 km of shoreline of the brittany coast this study examined the fate of amoco cadiz oil which entered the intertidal zone biodegradation by indigenous microbial populations was an extremely important process in the weathering of the oil alkanes were preferentially degraded but branched alkanes and polynuclear aromatic compounds also were subject to microbial attack the chemical evolution of the residual hydrocarbon mixture within the littoral zone led to a relative enrichment of isoprenoid alkanes naphtheno aromatic and napthenic compounds alkylated phenanthrenes aromatic organic sulfur compounds e g dibenzothiophenes hopanes and c 27 c 31 alkanes these classes of compounds appear to be most resistant to biological and chemical weathering continued inputs of relatively unweathered oil which may be preserved in subsurface anaerobic sediments and pooling of oil becomes increasingly important with time producing a patchy distribution of oil which has been weathered to varying degrees the presence of hydrocarbons within the littoral zone as a highly weathered residual oil appears to be a long lived multi year phenomenon

molybdenum isotope fractionation during adsorption by manganese oxides the isotopic composition of mo 97 95mo in seawater is 2 heavier than mo in marine ferromanganese crusts and nodules barling et al earth planet sci lett 193 2001 447 457 siebert et al earth planet sci lett 211 2003 159 171 to explore this phenomenon we have conducted an experimental investigation into the mass dependent fractionation of mo isotopes during adsorption onto mn oxyhydroxide two series of experiments were carried out a time series in which adsorption proceeded for 2 96 h and a ph series in which ph varied from 6 5 to 8 5 the extent of mo adsorption by mn oxyhydroxides decreases with increasing ph a trend typical of anion adsorption and takes 48 h to reach steady state lighter mo isotopes are preferentially adsorbed experimentally determined fractionation factors soln mnox exhibit no systematic variation with either time or experimental ph the mean soln mnox for all experiments is 1 0018 0 0005 2 s d comparison of the mo isotopic data for experimental solutions and mo adsorbed to mn oxyhydroxide with predictions for closed system equilibrium and rayleigh fractionation models indicates that isotope fractionation occurs as a result of closed system equilibrium exchange between dissolved and adsorbed mo the isotopic offset between dissolved and adsorbed mo is comparable to that observed between mo in seawater and mo in ferromanganese nodules and crusts it is therefore likely that adsorption of mo to mn oxyhydroxides is a significant factor in the fractionation of mo isotopes in the oceans

mierobial biogeochemistry and heterotrophy in sediments of a marine hydrocarbon seep vertical profiles of sediment and pore water constituents and rates of microbially mediated geochemical processes were determined in surficial sediments o 7 cm depth of three stations in and around isla vista hydrocarbon seep off santa barbara california measurements were made of pore water alkalinity total and carbonate ph eh dissolved oxygen sulfate and sulfide total sedimentary organic carbon toc and nitrogen atp sulfate reduction and dark bicarbonate uptake and incorporation and oxygen flux across the sediment water interface in benthic chambers in general alkalinity ph sulfide toc atp and all rate processes were greatest in sediments of that station a with active seepage and decreased with increasing distance from the seep sulfate depletion and extremely low eh values occurred in station a sediments at a station b with lower seepage rates than station a sedimentary and pore water constituents and rate processes were intermediate to those measured at station a and a station c without seepage pore water and sedimentary constituents as well as oxygen flux were strongly correlated with total extractable sedimentary hydrocarbons teh measured at each station and for each corresponding depth interval all parameters exhibited seasonal differences that may have been temperature dependent the greater concentrations of teh sulfide and alkalinity with increasing sedimentary depth indicate that seep sediments are a source of these constituents to the water column and a sink for 0 and s0 2 the strong heterotrophic and possibly chemoautotrophic character of seep sediments resembles that of other organically enriched systems the diagenesis of petroleum hydrocarbons is a function of the biogeochcmical patterns and microbial heterotrophic activities in surficial sediments

latest holocene evolution and human disturbance of a channel segment in the hudson river estuary abstract the latest holocene sedimentary record of a cohesive channel and subtidal shoal in the lower hudson river estuary was examined to elucidate natural sea level rise sediment transport and anthropogenic bulkheading dredging influences on the recent morphodynamic evolution of the system to characterize the seafloor and shallow subbottom 100 km of high resolution seismic reflection profiles chirp were collected within a 20 km reach of the estuary and correlated with sediment lithologies provided by eight vibracores recovered along seismic lines sediment geochronology with 137cs and 14c was used to estimate intermediate and long term sedimentation rates respectively and historical bathymetric data were analyzed to identify regional patterns of accretion and erosion and to quantify changes in channel geometry and sediment volume the shoal lithosome originated around 4 ka presumably with decelerating eustatic sea level rise during the latest holocene long term sedimentation rates on the shoal 2 3 2 6 mm yr are higher than in the channel 2 mm yr owing to hydrodynamic conditions that preferentially sequester suspended sediment on the western side of the estuary as a result the shoal accretes oblique to the principal axis of tidal transport and more rapidly than the channel to produce an asymmetric cross section shoal deposits consist of tidally bedded muds and are stratified by minor erosion surfaces that seismic profiles reveal to extend for 10s of meters to kilometers the frequency and continuity of these surfaces suggest that the surficial shoal is catastrophically stripped on decadal centennial time scales by elevated tidal flows tidal erosion maintains the shoal at a uniform depth below sea level and prevents it from transitioning to an intertidal environment consequently the long term sedimentation rate approximates the rate of sea level rise in the lower estuary 1 3 mm yr after the mid 1800s the natural geometry of the lower hudson river estuary changed rapidly in response to engineering works that forced the channel to self deepen analysis of historical bathymetric data indicates that the channel lost an estimated 3 106 tons of sediment between ca 1939 and 2002 50 000 tons yr average by subaqueous erosion increasing in depth by as much as 4 m in places erosion appears to have been concurrent with systematic bulkheading of the shoreline after ca 1865 which decreased the estuary surface area by 19 overall evidently self deepening of the channel is a morphodynamic adjustment to reestablish equilibrium cross sectional area yet the state of this change locally and elsewhere in the estuary is unknown subaqueous erosion documented in this study is a significant source of sediment with implications to the sediment budget and environmental quality of the hudson river estuary

holocene environmental change in the inner severn estuary uk an example of the response of estuarine sedimentation to relative sea level change holocene sediments of the wetlands around the inner severn estuary uk demonstrate a consistent stratigraphy of a single woody peat layer up to at least 4 5 m thick capped with a grey silty cla

rates of sediment accumulation in a tidal freshwater marsh abstract rates of sediment accumulation were determined for a delaware river tidal freshwater marsh utilizing radiometric palynological and sediment flux estimating techniques plus historical reviews all techniques showed good agreement indicating that tidal freshwater marshes are capable of preserving evidence of processes and events that have shaped the estuary through time prior to 1940 the marsh was a slowly accreting swamp accumulating material at the rate of 0 04 cm yr 1 prior to colonization of the region in the late 1600s and a somewhat more accelerated rate of 0 12 cm yr 1 prior to the introduction of regular tides in 1940 between 1940 and 1988 average rates of accumulation ranged between 1 04 and 1 38 cm yr 1 being highest near the tidal channe during the period 1954 65 rates averaged 1 67 cm yr 1 due to increased storm activity since 1966 storm activity has decreased and sediment accumulation rates have averaged 0 97 cm yr 1 reflecting these changes the current average rate of accumulation is four times the rate of sea level rise for this region of the estuary it is hypothesized that sediment accumulation will continue to exceed sea level rise until the marsh surface approximates mean high water

late pleistocene drainage systems beneath delaware bay abstract analyses of an extensive grid of seismic reflection profiles along with previously published sedimentary data and geologic information from surrounding coastal areas outline the ancestral drainage systems of the delaware river beneath lower delaware bay major paleovalleys within these systems have southeast trends relief of 10 35 m widths of 1 8 km and axial depths of 31 57 m below present sea level the oldest drainage system was carved into miocene sands probably during the late illinoian lowstand of sea level it followed a course under the northern half of the bay continued beneath the cape may peninsula and extended onto the present continental shelf this system was buried by a transgressive sequence of fluvial estuarine and shallow marine sediments during sangamonian time at the height of the sangamonian sea level transgression littoral and nearshore processes built the cape may peninsula southward over the northern drainage system and formed a contiguous submarine sedimentary ridge that extended partway across the present entrance to the bay when sea level fell during late wisconsinan time a second drainage system was eroded beneath the southern half of the bay in response to the southerly shift of the bay mouth this system which continued across the shelf was cut into coastal plain deposits of miocene and younger age and included not only the trunk valley of the delaware river but a large tributary valley formed by the convergence of secondary streams that drained the delaware coastal area during the holocene rise of sea level the southern drainage system was covered by a transgressive sequence of fluvial estuarine and paralic deposits that accumulated due to the passage of the estuarine circulation cell and to the landward and upward migration of coastal sedimentary environments some holocene deposits have been scoured subsequently by strong tidal currents the southward migration of the ancestral drainage systems beneath delaware bay is analogous to that found under nearby chesapeake bay in both areas shifts in the bay mouths and river courses have preserved the morphologies and sedimentary fill of former drainage systems and provided a clear record of major sea level fluctuations data from this study demonstrate that important information concerning ancient estuarine environments can be derived from the locations and characteristics of former fluvial systems

modern sedimentary environments in a large tidal estuary delaware bay abstract data from an extensive grid of sidescan sonar records reveal the distribution of sedimentary environments in the large tidally dominated delaware bay estuary bathymetric features of the estuary include large tidal channels under the relatively deep 10 m water depth central part of the bay linear sand shoals 2 8 m relief that parallel the sides of the tidal channels and broad low relief plains that form the shallow bay margins the two sedimentary environments that were identified are characterized by either 1 bedload transport and or erosion or 2 sediment reworking and or deposition sand waves and sand ribbons composed of medium to coarse sands define sites of active bedload transport within the tidal channels and in gaps between the linear shoals the sand waves have spacings that vary from 1 to 70 m amplitudes of 2 m or less and crestlines that are usually straight the orientations of the sand waves and ribbons indicate that bottom sediment movement may be toward either the northwest or southeast along the trends of the tidal channels although sand wave asymmetry indicates that the net bottom transport is directed northwestward toward the head of the bay gravelly coarse grained sediments which appear as strongly reflective patterns on the sonographs are also present along the axes and flanks of the tidal channels these coarse sediments are lag deposits that have developed primarily where older strata were eroded at the bay floor conversely fine sands that compose the linear shoals and muddy sands that cover the shallow bay margins appear mainly on the sonographs either as smooth featureless beds that have uniform light to moderate shading or as mosaics of light and dark patches produced by variations in grain size these acoustic and textural characteristics are the result of sediment deposition and reworking data from this study 1 support the hypothesis that bed configurations under deep tidal flows are functions of current velocity sediment size and depth 2 suggest criteria that could be used to distinguish between open estuarine tidal deposits in the geologic record and 3 provide a guide to future utilization of the bay floor

decadal link between longitudinal morphological changes in branching channels of yangtze estuary and movement of the offshore depo center in estuaries the morphology of inland and offshore areas usually evolves synergistically this study examines the decadal link between longitudinal changes in morphology of branching channels and movement of the offshore depo center where sediment deposition rate is maximum of the yangtze river estuary under intense human interference integrated data analysis is provided on morphology runoff discharge and ebb partition ratio from 1950 to 2017 channel volume reductions and change rates between isobaths in branching channels reflect the impact of estuarine engineering projects ebb partition ratio and duration of discharge 60 000 m3 s 1 act as proxies for the water excavating force in branching channels and runoff intensity it is found that deposition occurs in the lower upper sub reaches or further downstream upstream channels of the inland north south branching channels and the offshore depo center moves southward or southeastward as runoff intensity grows the reverse occurs as runoff intensity declines this is because the horizontal circumfluence in the yangtze estuary rotates clockwise as ebb partition ratios of the north south branching channels increase decrease for increasing runoff and conversely rotates anticlockwise for decreasing runoff land reclamation activities the deepwater channel project and the qingcaosha reservoir have impacted greatly on longitudinal changes of morphology in the north branch and the south passage and on ebb partition ratio variations in the north south channel and the north south passage dam induced runoff flattening has enhanced deposition in the upper lower sub reaches of the north south branching channels and caused northward movement of the offshore depo center except in areas affected by estuarine engineering projects dam induced longitudinal evolution of branching channel morphology and offshore depo center movement will likely persist in the future given the ongoing construction of large cascade dams in the upper yangtze and the completion of major projects in the yangtze estuary

hydrocarbons in bivalve mollusks of port valdez alaska consequences of five years permitted discharge petroleum hydrocarbons were investigated in mytilus edulis and macoma balthica at six intertidal sites in port valdez alaska after three to five years of oil terminal operation information about the concentrations of total hydrocarbons unresolved complex mixture normal alkanes isoprenoids olefins hopanes and polycyclic aromatic hyrocarbons shows that petroleum accumulation in these bivalve mollusks is greatest at the valdez municipal boat harbor and a crude oil terminal which has been permitted to discharge 170 kg oil day 1 accumulation two to ten fold less were observed at 3 km from the terminal and boat harbor the temporal trends in petroleum hydrocarbon concentrations in m edulis and m balthica reflect the effects of selective retention and depuration of different hydrocarbon classes as well as variation in hydrocarbon sources it is not clear whether the petroleum concentrations in port valdez bivalves had reached steady state by 1982 the final sampling time reported here