sediment contributions from floodplains and legacy sediments to piedmont streams of baltimore county maryland abstract disparity between watershed erosion rates and downstream sediment delivery has remained an important theme in geomorphology for many decades with the role of floodplains in sediment storage as a common focus in the piedmont province of the eastern usa upland deforestation and agricultural land use following european settlement led to accumulation of thick packages of overbank sediment in valley bottoms commonly referred to as legacy deposits previous authors have argued that legacy deposits represent a potentially important source of modern sediment loads following remobilization by lateral migration and progressive channel widening this paper seeks to quantify 1 rates of sediment remobilization from baltimore county floodplains by channel migration and bank erosion 2 proportions of streambank sediment derived from legacy deposits and 3 potential contribution of net streambank erosion and legacy sediments to downstream sediment yield within the mid atlantic piedmont we calculated measurable gross erosion and deposition rates within the fluvial corridor along 40 valley segments from 18 watersheds with drainage areas between 0 18 and 155 km2 in baltimore county maryland we compared stream channel and floodplain morphology from lidar based digital elevation data collected in 2005 with channel positions recorded on 1 2400 scale topographic maps from 1959 1961 in order to quantify 44 46 years of channel change sediment bulk density and particle size distributions were characterized from streambank and channel deposit samples and used for volume to mass conversions and for comparison with other sediment sources average annual lateral migration rates ranged from 0 04 to 0 19 m y which represented an annual migration of 2 5 0 9 4 4 channel width across all study segments suggesting that channel dimensions may be used as reasonable predictors of bank erosion rates gross bank erosion rates varied from 43 to 310 mg km y median 114 and were positively correlated with drainage area measured deposition within channels accounted for an average of 46 28 75 of gross erosion with deposition increasingly important in larger drainages legacy sediments accounted for 6 90 of bank erosion at individual study segments represented about 60 of bank height at most exposures and accounted for 57 16 of the measured gross erosion extrapolated results indicated that first and second order streams accounted for 62 38 of total streambank erosion from 1005 km2 of northern baltimore county after accounting for estimated redeposition extrapolated net streambank sediment yields 72 mg km2 y constituted 70 of estimated average piedmont watershed yields 104 mg km2 y the results suggest that streambank sediments are a relatively large source of sediment from piedmont tributaries to the chesapeake bay

orbital control on carbon cycle and oceanography in the mid cretaceous greenhouse we established a new high resolution carbonate carbon isotope record of the albian interval of the marne a fucoidi formation central apennines italy which was deposited on the southern margin of the western tethys ocean bulk carbonate sampled with 10 15 cm spacing was used for the construction of a continuous carbon isotope curve through the albian stage spectral analyses reveal prominent 400 kyr cyclicity in the 13c curve which correlates with milankovitch long eccentricity changes cycles occurring in our record resemble those observed in several cenozoic 13c records suggesting that a link between orbital forcing and carbon cycling existed also under mid cretaceous greenhouse conditions based on comparisons with cenozoic eccentricity carbon cycle links we hypothesize that 400 kyr cycles in the mid cretaceous were related to a fluctuating monsoonal regime coupled with an unstable oceanic structure which made the oceanic carbon reservoir sensitive to orbital variations in the tethys these oceanographic conditions lasted until the late albian and then were replaced by a more stable circulation mode less sensitive to orbital forcing

channel adjustments following two dam removals in wisconsin 1 we examined channel response following the removal of low head dams on two lowgradient fine to coarse grained rivers in southern wisconsin following removal channels eroded large quantities of fine sediment resulting in deposition 3 5 km downstream at one site baraboo river upstream changes were rapid and included bed degradation minimal bank erosion and sediment deposition on channel margins and new floodplain sand was transported through the former impoundment and temporarily deposited downstream at the second site koshkonong river head cut migration governed channel adjustments a deep narrow channel formed downstream of the headcut with negligible changes upstream of the head cut fluvial changes were summarized in a conceptual channel evolution model that highlighted 1 similarities between adjustments associated with dam removal and other events that lower channel base level and 2 the role of reservoir sediment characteristics particle size cohesion in controlling the rates and mechanisms of sediment movement and channel adjustment index terms 1815 hydrology erosion and sedimentation 1824 hydrology geomorphology 1625 1857 hydrology reservoirs surface keywords dams dam removal channel evolution model

evolution of the lower saxony basin abstract the lower saxony basin is a 300 km long and 65 km wide late jurassic and early cretaceous trough which parallels the northern margin of the rhenish massif this basin became inverted during the senonian and paleocene the lower saxony basin is the most important oil province of germany past production amounts to 200 10 6 t of oil 1 5 10 9 bbl the lower saxony basin is superimposed on the late carboniferous variscan foredeep basin and the frontal structures of the variscan fold belt during the permian to middle jurassic the area formed part of the northwest european basin differential subsidence of the lower saxony basin was initiated during the late jurassic and persisted till albian time this involved reactivation of permo carboniferous fracture systems by divergent wrenching a major aptian deep seated laccolith is evident in the western part of the lower saxony basin during the senonian and paleocene sinistral convergent wrenching induced uplift of the basin floor and folding of its sedimentary fill the margins of the inverted lower saxony basin are thrust over the adjacent stable platform areas the differential subsidence of the lower saxony basin can be related to a period of major crustal extension in the north sea rift basin inversion coincides with important orogenic events in the alpine system and is thought to have been induced by intra plate compressional stresses

remarks on the identification of the albian cenomanian boundary and taxonomic clarification of the planktonic foraminifera index species globotruncanoides brotzeni and tehamaensis the planktonic foraminifera assemblage across the global boundary stratotype section and point gssp for the base of the cenomanian stage defined at mont risou haute alpes in france is here restudied to clarify the identification and stratigraphic distribution of thalmanninella globotruncanoides rotalipora globotruncanoides sigal 1948 and pseudothalmanninella tehamaensis rotalipora tehamaensis marianos zingula 1966 whose appearance levels are primary and secondary criteria for placing the albian cenomanian boundary since the ratification of the gssp in 2002 the identification of the foraminifera index species across the albian cenomanian boundary has been reported to be sometimes difficult either because of their rarity or uncertainty in the taxonomic identifications we discuss the taxonomic status of thalmanninella brotzeni sigal 1948 a species regarded for a long time to be a junior synonym of th globotruncanoides through images of sigal9s type materials deposited at the musee national d histoire naturelle paris and elucidate the taxonomically important characters that enable unequivocal identification of th brotzeni th globotruncanoides and ps tehamaensis planktonic foraminifera marker species from mont risou are compared with well preserved specimens from blake nose plateau odp 171b north western atlantic ocean to verify the reliability and stratigraphic distribution of these marker taxa outside the mediterranean tethyan area

equilibrium or indeterminate where sediment budgets fail sediment mass balance and adjustment of channel form green river downstream from flaming gorge dam utah and colorado this study examines bed and bank adjustment in the 105 km reach of the green river immediately downstream from flaming gorge dam by the use of historical aerial and oblique photographs analysis of current and abandoned stream gaging records and field observations although this segment has been previously characterized as sediment deficient these data show that sediment is accumulating in all reaches and that the bed has not degraded at any location where historical data are available adjustment is occurring through a combination of deposition of post dam sediment and stabilization of pre dam deposits resulting in a 10 30 reduction in average width of the channel all post dam surfaces are colonized by woody riparian vegetation the style of channel adjustment varies between geomorphically defined reaches in canyons dominated by debris fans and gravel bedded restricted meandering reaches gravel bars have become inactive and accumulated fine sediment in the sand bedded meandering reaches existing islands have increased in size and new mid channel islands have formed in all of these types of reaches post dam deposits line the banks and sediment has accumulated in side channels that previously separated islands from the bank these findings demonstrate that sediment budgets that show a balance between inputs and outputs cannot necessarily be interpreted to indicate channel equilibrium a sediment mass balance for 150 km reach between the dam and the first long term gage indicates approximate balance of inputs and outputs for the pre and post dam periods when uncertainty in budget components is considered the mass balance is indeterminate although the green river may have been in approximate equilibrium in the pre dam period we have shown that channel width is decreasing in the post dam period the post dam deposits constitute a small but a significant component of the sediment budget upstream from the first major tributary sediment is supplied to this reach by small tributaries and to a lesser extent erosion of pre dam alluvium downstream from the study area the volume of the post dam deposits is tiny relative to the volume of sediment input from the first major tributary d 2005 elsevier b v all rights reserved

genesis of disseminated sulphide assemblages in niagara peninsula canada in the niagara peninsula of southern ontario canada subeconomic occurrences of mississippi valley type base metal assemblages are found in the petroliferous carbonate units of the middle silurian sedimentary succession these units which were deposited on the northwestern margin of the appalachian basin were buried by about 2 4 km of paleozoic sediments up to the time of the appalachian orogeny

the kirchrode i and ii boreholes technical details and evidence on tectonics and the palaeoceanographic development during the albian abstract the technical details of drilling and coring at the kirchrode i and ii sites are presented at these sites a sequence of claystones and marlstones from an albian shelf basin was recovered constraints on the ages of the sediments in the two boreholes are provided by the occurrence of the inoceramid bivalve actinoceramus sulcatus the first appearance of which is used to define the middle upper albian boundary and by observed facies changes that can be correlated to the established lithostratigraphy the cores from the two boreholes provide a rather complete 285 m long sequence of the upper albian with a 155 5 m long overlap analysis of the tectonic structures showed considerable shortening in the middle and lower albian part of the sequence due to normal faulting of the upper albian only the lowermost part is affected by faults the increase in sedimentation rates of terrigenous detritus and of marine biogenic carbonate which occurs in the basal part of the c auritus subzone is interpreted to reflect a regional change to a more humid climate and regional tectonic movements uplift of the rhenish bohemian massif subsidence of the lower saxony basin intensified locally by halokinetic movements the further increase in marine productivity in the latest albian may be related to upwelling of more nutrient rich deep water along submarine relief in this shelf sea identification of milankovitch cyclicity documented by the fluctuating caco3 contents of the sediments is used i to constrain the minimum time represented by the upper albian deposits and ii to determine the duration of the sea level cycles cycle v 1 6 ma cycle vi 2 ma and iii to establish the duration of the late albian ammonite subzones e g callihoplites auritus subzone 2 1 ma average sedimentation rates determined from the identified 100 ka eccentricity cycles show a stepwise increase in sedimentation rates from 1 2 cm 1000 a in the lower albian dark claystones to 7 13 cm 1000 a in the late late albian in addition to the general deepening trend through the late albian two nearly completely documented 3rd order sea level cycles in the upper albian of kirchrode i were recognised plus another one cut short by faulting at the base of the upper albian documented in kirchrode ii these global sea level cycles were identified on the basis a of the sequence of the abundance maxima of selected benthos and plankton groups b of trends in the fluctuations of the caco3 content and c of the abundance of glauconite the transgression periods in this upper albian deep shelf basin are characterised by intensified circulation this intensified circulation is found to have affected first the surface near waters resulting e g in an increase in the abundance of immigrant plankton and nekton species from the tethys at a later stage the deep water was affected supporting then an increased population of suspension feeding benthos and causing condensation and erosion in the sediment at the sea floor

present day precipitation of lead and zinc from groundwaters small quantities of galena and sphalerite are currently precipitating 26m below the surface at the vinemount quarry ontario canada from sulfurous spring waters issuing from carbonates of the lockport formation at the spring orifices these sulfides are present in both fracture coatings and an associated black sludge these precipitates are overlain by a crust rich in native sulfur the mineralogy of the precipitates and the chemistry of waters taken from three consistent spring horizons indicates that downward moving meteoric groundwaters leach metals from the host rocks and precipitate galena and sphalerite on encountering h2s rich waters at the water table while our observation of the transport and deposition of lead and zinc by shallow groundwaters lends support to intra karstic models for the direct precipitation of galena and sphalerite it also enables us to propose that many carbonate hosted pb zn deposits of differing theories of origin may have been enriched during periods of uplift

mid cretaceous oceanic anoxic events in the pacific ocean revealed by carbon isotope stratigraphy of the calera limestone california usa the paleoceanographic history of the pacific ocean during the mid cretaceous is poorly constrained due to the loss of much of the contemporaneous pacific seafloor to subduction and difficulties in recovering chert rich sediments by ocean drilling pelagic sediments that were originally deposited in the pacific ocean but that have been subsequently accreted during subduction potentially provide an alternative paleoceanographic archive this study presents micropaleontological and carbon isotope data from the calera limestone part of the classic franciscan complex exposed in permanente quarry central california usa in the three stratigraphic sections studied pelagic limestones with low organic carbon contents are the dominant lithology however two stratigraphic intervals are recognized that contain organic carbon and these date to the early aptian and late albian early cenomanian these time intervals correspond to two mid cretaceous oceanic anoxic events oaes early aptian oae1a equivalent to the selli level and late albian oae1d equivalent to the breistroffer event it is well established that both of these events were associated with significant carbon isotope excursions which are also shown to exist in the calera limestone the record of oae1a from the calera limestone complements ocean drilling records by providing further evidence for variability in the sedimentary and stratigraphic record of this event the carbon isotope data from the late albian early cenomanian provide the first detailed chemobiostratigraphic record of this period for the pacific ocean confirming that environmental change occurred at this time in the pacific possibly related to oae1d

minor changes in surface water fertility across the oceanic anoxic event 1d latest albian se france evidenced by calcareous nannofossils the latest albian sediments deposited in the vocontian basin in south eastern france record the oceanic anoxic event oae 1d locally named the breistroffer interval they are represented by argillaceous marls and marls containing organic matter total organic carbon varying from 0 8 to 1 changes in calcareous nannofossil abundance and assemblage composition as well as macrofauna abundance ichnofossil assemblage and bioturbation intensity were analysed in order to evaluate the main palaeoenvironmental factors controlling the deposition of the oae 1d sediments in this area the pelagic carbonate production is limited and the carbonate fraction is predominantly of nektonic benthic and of allochthonous origin from carbonate platforms the enrichment in organic carbon within the breistroffer interval is weak and not associated with high surface water productivity the organic matter is mainly terrigenous its record is due to 1 a good preservation under dysoxic conditions within the sediments and 2 a weak input of allochthonous carbonates eustatic fluctuations strongly influenced the variations of nannofossil and macrofauna abundances distinctive patterns in nannofossil assemblages and macrofauna abundances within the breistroffer interval are also recognized reflecting changes from mesotrophic to more oligotrophic conditions which are probably controlled by climate

evolution patterns of radiolaria and organic matter variations a new approach to identify sea level changes in mid cretaceous pelagic environments the relation between sea level changes plankton productivity and evolution as well as the occurrence of anoxic sediments provides an interesting avenue of paleooceanographic research in this context we examined mid cretaceous radiolarian faunas carbonate isotopic and organic matter type data of deep sea drilling project and ocean drilling program cores from the north atlantic and samples from outcrops of the western tethys from central and northern italy former studies indicate that an expansion of the oxygen minimum zone caused plankton extinctions at the cenomanian turonian boundary an expanded oxygen minimum zone would destroy deeper habitats of planktic foraminifera causing the extinction of deeper dwelling forms although this model is well established for the cenomanian turonian boundary not much is known about the causes of extinctions and radiations during the entire mid cretaceous aptian turonian we demonstrate that the dimension of the oxygen minimum zone which depends on the relative sea level and the corresponding nutrient supply causes the complex pattern of evolution and radiation of planktic protozoa and the sedimentation of black shales in the mid cretaceous this new depositional model allows correlation of micropaleontologic data and different types of black shales in the pelagic realm within a sequence stratigraphic framework

the albian cenomanian transition and oceanic anoxic event 1d an example from the boreal realm the upper albian to lower cenomanian interval in the hanover area germany is characterized by a well developed lithological transition from upper albian monotonous marly claystones of several hundred metres thickness which become enriched in biosilica in the topmost albian to increasingly caco3 rich marls and limestones in the lower and middle cenomanian this study presents a new 165 m thick composite record spanning the latest albian to mid early cenomanian ca 103 0 to 97 5 ma based on two core drillings at anderten in the central lower saxony basin east of hanover which is a sub basin of the north german basin due to the lack or delayed occurrences of tethyan biostratigraphic markers for the late albian and early cenomanian in the boreal realm the definition of the albian cenomanian boundary as based on the lowest occurrence of thalmanninella globotruncanoides is not applicable in order to overcome this issue an integrated biostratigraphic chemostratigraphic approach has been employed in addition to biostratigraphy calcareous nannofossils ostracods planktonic foraminifera and inoceramids the anderten succession has been studied using sedimentary geochemistry caco3 total organic carbon toc 13c and 18o ray logging and x ray fluorescence core scanning this approach enabled successful correlation of the composite anderten record to european reference sections in england south east france and italy as well as to further low resolution records from the lower saxony basin wunstorf and konrad 101 core this work has made it possible to identify the 13ccarb expression of i the oceanic anoxic event 1d ii the albian cenomanian boundary interval and iii potentially the lower cenomanian event s chemostratigraphic age assignments are supported by biostratigraphic results calcareous nannofossils indicate an extended upper cretaceous 0 uc0 zone upper albian up to uc2 upper lower cenomanian and the occurrence of the ostracod physocythere steghausi supports an early cenomanian age for most of the upper part of the composite record notably influxes of the planktonic foraminifer thalmanninella aff reicheli have previously been described from this area and the first appearance of this taxon is usually used to define the base of the middle cenomanian substage however findings from the anderten cores and elsewhere suggest that this taxon has an apparently earlier first appearance questioning previous age assignments from the boreal realm solely based on planktonic foraminifera due to both moderately well preserved microfossils and high sedimentation rates the drilled succession of anderten is considered as a potential boreal reference section for the albian cenomanian transition this article is protected by copyright all rights reserved

relative sea level change and carbon isotopes data from the upper jurassic oxfordian of central and southern europe studies on cretaceous pelagic limestones have shown a close correspondence between putative sea level curves and the carbon isotope profile suggesting a possible relationship between the two phenomena such a relationship could relate to shelf sea area governing the global burial rate of organic carbon which in turn controls the 13c 12c ratio of dissolved inorganic carbon in the oceanic reservoir in order to see whether or not this relationship might be of more general applicability the major mid oxfordian jurassic transgression is documented to zonal level and appropriate carbon isotope data are presented although the applicability of ammonite zonation to the mid oxfordian is problematic on a regional scale a clear 13c excursion is present in the trunsversariurn zone which is coincident with regional overstep and or evidence of shoreline retreat and or evidence of bathymetric deepening in europe and elsewhere the use of the carbon isotope curve as a proxy for shelf sea area or relative sea level is worthy of further exploration

increased mid twentieth century riverbank erosion rates related to the demise of mill dams south river virginia a recent hypothesis suggests that fluvial processes in areas of the eastern united states are strongly influenced by the demise of colonial mill dams rather than reflecting a quasi equilibrium adjustment to the current hydrologic and sediment regime we evaluated the control of colonial mill dams on twentieth and twenty first century bank erosion rates on the south river virginia through studies of historical aerial photographs historical documents hydrologic and climatic records and hydraulic modeling historical sources and aerial photographs document eight colonial mill dams along the study reach in the early twentieth century all but one of these dams disappeared in the 1950s and the last was breached by 1976 from initially low values between 1937 and 1957 mean bank erosion rates increased by more than a factor of 2 after 1957 remaining high through 2005 accelerated bank erosion rates cannot be explained by changes in storm intensity the frequency of freeze thaw cycles or by changes in the density of riparian trees hydraulic modeling suggests that mill dams reduced velocities of the 5 yr flood through 80 of our study reach by considering the timing of mill dam loss the spatial extent of backwater influence and the locations of our study sites we find that the loss of mill dams explains the observed trends in bank erosion rates at 9 and possibly 10 of our 14 monitoring sites these results support the hypothesis that the demise of mill dams has been an important influence on fluvial processes in the region

late albian ammonite biostratigraphy of the kirchrode i borehole hannover germany abstract the ammonite biostratigraphy of the 245 m of sediments of late albian age traversed in the kirchrode i 1 91 boring situated in the south eastern suburbs of the city of hannover lower saxony basin is described correlation is made with the actinoceramus birostrina bivalve biostratigraphy in the part of the core of early late albian age and with the inoceramus inoceramus lissa aucellina gryphaeoides succession above the earliest sediments of late albian age are of late dipoloceras cristatum subzone age with a good representation of the hysteroceras orbignyi subzone and an incomplete representation of the hysteroceras varicosum subzone a notable feature of the succession is the presence of a considerable thickness ca 164 m of sediments of callihoplites auritus subzone age sediments of stoliczkaia dispar zone age indicate the representation of the mortoniceras mortoniceras rostratum mortoniceras durnovarites perinflatum and arrhaphoceras praeschloenbachia briacensis subzones the ammonite fauna of the borehole is listed and the ammonite biostratigraphy of the clay sediments traversed is discussed a brief comparison is made with other surface and borehole sections in northern germany and elsewhere and the more cosmopolitan tethyan elements of the fauna are indicated and discussed

bank erosion of legacy sediment at the transition from vertical to lateral stream incision streambank erosion is a primary source of suspended sediments in many waterways of the us atlantic piedmont this problem is exacerbated where banks are comprised of fine sediment produced by the intensive land use practices of early european settlers a stream in this region richland creek incises into banks comprised of three stratigraphic layers associated with historic land use pre european settlement early european agriculture and development and water powered milldam operation this study aims to identify the bank processes along a reach of richland creek that is eroding towards its pre disturbance elevation the volume of material that has eroded along this stream since the milldam breached was calculated by differencing a reconstructed surface of the pond bed and an aerial lidar digital terrain model dtm immediately downstream from the study reach the channel is floored by bedrock and immediately upstream the rate of channel erosion approximately doubled along the longitudinal profile of richland creek which indicate that the study reach spans the transition from a channel dominated by vertical incision in the upstream direction to horizontal widening in the downstream direction the combined hydrometeorological conditions and dominant processes causing reach scale cut bank erosion were investigated with analyses of stream stage precipitation and streambank volumetric and surfaces change that was measured during nine terrestrial lidar surveys in 2010 2012 the spatial variability of erosion during a simulated precipitation event was examined in a field based experiment erosion was greatest where mill pond sediment columns detached along vertical desiccation and horizontal seepage cracks this sediment accumulated on the bank toe throughout the study and was a source of readily entrained fine sediment contrary to the upper reaches where depositional accommodation space is more limited findings suggest that hotspots of sediment excavation progress upstream indicating that restoration efforts should focus upon stabilizing banks at these locations copyright 2015 john wiley sons ltd

mesozoic climates and oceans a tribute to hugh jenkyns and helmut weissert the study of past greenhouse climate intervals in earth history such as the mesozoic is an important relevant and dynamic area of research for many sedimentary geologists geochemists palaeontologists and climate modellers the mesozoic sedimentary record provides key insights into the mechanics of how the earth system works under warmer conditions providing examples of natural climate change and perturbations to ocean chemistry including anoxia that are of societal relevance for understanding and contextualizing ongoing and future environmental problems furthermore the deposition of widespread organic carbon rich sediments black shales during the mesozoic means that this is an era of considerable economic interest in july 2015 an international group of geoscientists attended a workshop in ascona switzerland to discuss all aspects of the mesozoic world and to celebrate the four decade long contributions to our understanding of this fascinating era in earth history made by hugh jenkyns university of oxford and helmut weissert eth zurich this volume of sedimentology arose from that meeting and contains papers inspired by and co authored by hugh and helmi here a brief introduction to the volume is provided that reviews aspects of hugh and helmi s major achievements contextualizes the papers of the thematic issue and discusses some of the outstanding questions and areas for future research this article is protected by copyright all rights reserved

late cretaceous intraplate thrusting in central europe effect of africa iberia europe convergence not alpine collision a well established event of intraplate basin inversion and basement thrusting affected central europe in late cretaceous time it is widely accepted to have resulted from the collision of the alpine orogen with europe s margin at that time an early alpine orogen located on the leading edge of the adria microplate still lay far southeast of its present day position and had entered a phase of extension after a first orogenic event characterized by w to nw directed thrusting this configuration is not likely to have induced ssw nne directed thrusting and folding in the future european foreland that was still separated from the alpine wedge by a strip of oceanic lithosphere by contrast the onset of intraplate contraction coincides with an important change in relative motion between the european and african plates at ca 90 ma africa s sse directed sinistral transform motion relative to europe changed to ne directed convergence this agrees well with the timing and kinematics of intraplate thrusting in central europe structures of similar age and kinematics occurring in southern france spain and north africa suggest that the late cretaceous pulse of contraction was caused by pinching west central europe s thin lithosphere between baltica and africa only since the onset of n directed thrusting in the alps in paleocene or eocene time are the kinematics of the alps and their european foreland compatible indicating that mechanical coupling between africa europe and the adria microplate had been achieved

knickpoint recession rate and catchment area the case of uplifted rivers in eastern scotland knickpoint behaviour is a key to understanding both the landscape responses to a base level fall and the corresponding sediment fluxes from rejuvenated catchments and must be accommodated in numerical models of large scale landscape evolution knickpoint recession in streams draining to glacio isostatically uplifted shorelines in eastern scotland is used to assess whether knickpoint recession is a function of discharge here represented by its surrogate catchment area knickpoints are identified using ds plots log slope versus log downstream distance a statistically significant power relationship is found between distance of headward recession and catchment area such knickpoint recession data may be used to determine the values of m and n in the stream power law e kamsn the data have too many uncertainties however to judge definitively whether they are consistent with m n 1 bedrock erosion is proportional to stream power and kps should be maintained and propagate headwards or m 0 3 n 0 7 bedrock incision is proportional to shear stress and kps do not propagate but degrade in place by rotation or replacement nonetheless the e scotland m and n values point to the dominance of catchment area discharge in determining knickpoint retreat rates and are therefore more consistent with the stream power law formulation in which bedrock erosion is proportional to stream power copyright 2005 john wiley sons ltd

warm tropical ocean surface and global anoxia during the mid cretaceous period the middle of the cretaceous period about 120 to 80 myr ago was a time of unusually warm polar temperatures1 repeated reef drowning in the tropics2 and a series of oceanic anoxic events oaes that promoted both the widespread deposition of organic carbon rich marine sediments and high biological turnover3 4 5 6 7 8 the cause of the warm temperatures is unproven but widely attributed to high levels of atmospheric greenhouse gases such as carbon dioxide7 8 9 10 11 12 in contrast there is no consensus on the climatic causes and effects of the oaes with both high biological productivity and ocean stagnation being invoked as the cause of ocean anoxia3 4 5 6 7 8 here we show using stable isotope records from multiple species of well preserved foraminifera that the thermal structure of surface waters in the western tropical atlantic ocean underwent pronounced variability about 100 myr ago with maximum sea surface temperatures 3 5 c warmer than today this variability culminated in a collapse of upper ocean stratification during oae 1d the breistroffer event a globally significant period of organic carbon burial that we show to have fundamental stratigraphically valuable geochemical similarities to the main oaes of the mesozoic era our records are consistent with greenhouse forcing being responsible for the warm temperatures but are inconsistent both with explanations for oaes based on ocean stagnation and with the traditional view reviewed in ref 12 that past warm periods were more stable than today s climate

the history of human induced soil erosion geomorphic legacies early descriptions and research and the development of soil conservation a global synopsis abstract this paper presents a global synopsis about the geomorphic evidence of soil erosion in humid and semihumid areas since the beginning of agriculture historical documents starting from ancient records to data from the mid twentieth century and numerous literature reviews form an extensive assortment of examples that show how soil erosion has been perceived previously by scholars land surveyors farmers land owners researchers and policy makers examples have been selected from ancient greek and roman times and from central europe southern africa north america the chinese loess plateau australia new zealand and easter island furthermore a comprehensive collection on the development of soil erosion research and soil conservation has been provided with a particular focus on germany and the usa geomorphic evidence shows that most of the agriculturally used slopes in the old and new worlds had already been affected by soil erosion in earlier prehistoric times early descriptions of soil erosion are often very vague with regard to the roman times geomorphic evidence shows seemingly opposing results ranging from massive devastation to landscapes remaining stable for centuries unfortunately historical documentation is lacking in the following centuries historical records become more frequent and more precise and observations on extreme soil erosion events are prominent sometimes they can be clearly linked to geomorphic evidence in the field the advent of professional soil conservation took place in the late eighteenth century the first extensive essay on soil conservation known to the western world was published in germany in 1815 the rise of professional soil conservation occurred in the late nineteenth and early twentieth centuries soil remediation and flood prevention programs were initiated but the long term success of these actions remains controversial in recent years increasing interest is to recover any traditional knowledge of soil management in order to incorporate it into modern soil conservation strategies the study shows that local and regional variations in natural settings cultural traditions and socioeconomic conditions played a major role for the dynamics and the rates of soil erosion on a long term perspective geomorphic evidence and historical sources can often complement each other but there should be also an awareness of new pitfalls when using them together

lithogeochemical patterns around pb zn mineralizations in dinantian carbonate rocks of eastern belgium the lithogeochemical distribution patterns of mg sr na zn pb fe mn k corg organic matter and ir insoluble residue in the dinantian limestones and dolomites from the eastern part of belgium have been studied dinant and verviers synclinorium comparison of geochemical data of non mineralized strata revealed higher background values in the strata of the verviers synclinorium where pb zn mineralizations occur in this area a relation may exist with the metallogenetic district herve vesdre theux district proposed by dejonghe 1985b however the higher background values also could relate to the more restricted sedimentation conditions in the verviers synclinorium as opposed to the more open marine conditions in the dinant synclinorium the influence of mineralization on the geochemistry of limestones is limited and unpredictable in dolomites however the effect can be important in these rocks the lithogeochemical distribution of zn pb and mn can be subdivided into three populations i e a regional background a local high background and a halo population the higher trace element concentrations in the halo population is caused by the existence of disseminated sulfide minerals sphalerite galena and pyrite and zn bearing goethite mainly pseudomorphs after pyrite and mn oxides the sulfides relate to the ore emplacement in the local high background only the zn bearing oxides occur their presence and thus the development of the local high background relates to weathering processes

the piedmont landscape of maryland a new look at an old problem the piedmont upland of maryland has been variously interpreted as a peneplain a series of peneplains a surface of marine planation and a landscape in dynamic equilibrium these different perspectives of landform evolution are related to different scales of time and space both equilibrium and episodic erosion features can be recognized in the modern landscape an equilibrium condition is suggested by adjustment of first and second order streams to rock structure and lithology entrenchment of some streams against gneiss domes altitudinal zonation of rock types around gneiss domes correlation of lithology with overburden thickness on uplands decreasing overburden thickness on uplands related to decreasing degree of metamorphism of crystalline rocks and correlation of secondary mineral assemblages with subsurface drainage and slope the long term episodic character of erosion is suggested by clastic wedges on the adjacent coastal plain an upland of low relief that truncates non carbonate rocks of different lithologies isovolumetric chemical weathering of alumino silicate rocks clastic deposition in marble valleys and weathering profile truncation by modern drainage the maryland piedmont may have been an area of positive relief subject to subaerial erosion since triassic and possibly permian time the upland surface preserved in the eastern piedmont developed by the late cretaceous in the interval from the late cretaceous to the late miocene low input of terrigenous sediments to the coastal plain dominance of marine sedimentation and spotty evidence of saprolite formation on crystalline rocks suggest that the maryland piedmont was an area of low relief undergoing intense weathering incised valleys were formed during a cycle of erosion probably initiated in the late miocene and extensive colluvial sediments were deposited on hillslopes by periglacial processes during the pleistocene

carbon and oxygen isotope stratigraphy of the english chalk and italian scaglia and its palaeoclimatic significance a detailed carbon and oxygen isotope stratigraphy has been generated from upper cretaceous coastal chalk sections in southern england east kent culver cliff isle of wight eastbourne and seaford head sussex norfolk coast and the british geological survey bgs trunch borehole norfolk data are also presented from a section through the scaglia facies exposed near gubbio italian apennines wherever possible the sampling interval has been one metre or less both the chalk and scaglia carbon isotopic curves show minor positive excursions in the mid cenomanian mid and high turonian basal coniacian and highest santonian lowest campanian there is a negative excursion high in the campanian in chalk sections that span that interval the well documented cenomanian turonian boundary spike is also well displayed as is a broad positive excursion centred on the upper coniacian a number of these positive excursions correlate with records of organic carbon rich deposition in the atlantic ocean and elsewhere the remarkable similarity in the carbon isotope curves from england and italy enables cross referencing of macrofossil and microfossil zones and pinpoints considerable discrepancy in the relative positions of the turonian coniacian and santonian stages the oxygen isotope values of the various chalk sections although showing different absolute values that are presumably diagenesis dependent show nonetheless a consistent trend the east kent section which is very poorly lithified indicates a warming up to the cenomanian turonian boundary interval then cooling thereafter regional organic carbon burial documented for this period is credited with causing drawdown of co 2 and initiating climatic deterioration inverse greenhouse effect data from other parts of the world are consistent with the hypothesis that the cenomanian turonian temperature optimum was a global phenomenon and that this interval represents a major turning point in the climatic history of the earth

reconstructing past sea surface temperatures correcting for diagenesis of bulk marine carbonate abstract a numerical model which describes oxygen isotope exchange during burial and recrystallization of deep sea carbonate is used to obtain information on how sea surface temperatures have varied in the past by correcting measured 18o values of bulk carbonate for diagenetic overprinting comparison of bulk carbonate and planktonic foraminiferal 18o records from odp site 677a indicates that the oxygen isotopic composition of bulk carbonate does reflect changes in sea surface temperature and 18o at odp site 690 we calculate that diagenetic effects are small and that both bulk carbonate and planktonic foraminiferal 18o records accurately reflect paleogene warming of high latitude surface oceans biased from diagenesis by no more than 1 c the same is likely to be true for other high latitude sites where sedimentation rates are low at dsdp sites 516 and 525 the effects of diagenesis are more significant measured 18o values of eocene bulk carbonates are more than 2 lower at deeply buried site 516 than at site 525 consistent with the model prediction that the effects of diagenesis should be proportional to sedimentation rate model corrections reconcile the differences in the data between the two sites the resulting paleotemperature reconstruction indicates a 4 c cooling of mid latitude surface oceans since the eocene at low latitudes the contrast in temperature between the ocean surface and bottom makes the carbonate 180 values particularly sensitive to diagenetic effects most of the observed variations in measured 18o values are accounted for by diagenetic effects rather than by sea surface temperature variations we show that the data are consistent with constant equatorial sea surface temperatures through most of the cenozoic with the possible exception of the early eocene when slightly higher temperatures are indicated we suggest that the lower equatorial sea surface temperatures for the eocene and oligocene reported in other oxygen isotope studies are artifacts of diagenetic recrystallization and that it is impossible to reconstruct accurately equatorial sea surface temperatures without explicitly accounting for diagenetic overprinting

reassessing the role of milldams in piedmont floodplain development and remobilization abstract recent emphasis on milldams as a cause of colonial era floodplain sediment deposits and source for modern remobilization has ignited debate in scientific and environmental policy forums especially in the mid atlantic usa although milldams are regionally ubiquitous and visually striking no investigation has demonstrated that they are a dominant driver of regional floodplain sediment accumulation and remobilization long term analysis in baltimore county maryland found that milldams were sufficient but not necessary for historical sediment accumulation we compared erosion from streams upstream and downstream of confirmed milldam locations in paired segment comparisons with and without the influence of historical milldams and pooled across 37 study segments we found the scale of inquiry produced different interpretations regarding the role of milldams in regional erosion and sedimentation although local milldam sediment remobilization rates were 15 greater than those immediately downstream neither paired nor pooled segment comparisons provided evidence that milldam deposits are contemporary dominant sources of sediment further comparison across drainage areas demonstrated that milldam deposits could raise local remobilization rates by augmenting sediment availability along supply limited channels we introduce a unifying conceptual model that explains apparently contradictory findings in the literature where rather than the sole cause of legacy sediment deposits some milldams are nonetheless responsible for local increases in sediment remobilization rates along portions of the stream network

upland sediment supply and its relation to watershed sediment delivery in the contemporary mid atlantic piedmont u s a abstract we use sediment accumulation in ponds and reservoirs to examine upland sediment sources and sinks in the piedmont physiographic region of maryland usa in zero order and first order watersheds sediment yield is greatest from suburban land cover followed by agriculture and forest the idea that sediment yield is small from mature suburban development appears to not be correct first order channel enlargement is an important sediment source causing sediment yield to increase from zero order to first order watersheds nonchannel sources provide one third to two thirds of the upland sediment load long term sediment accumulation in a reservoir at fifth order indicates that cumulative sediment load from upland areas is reduced by one quarter by net valley bottom sedimentation if upland supply exceeds the load delivered from a watershed sediment must accumulate along valley bottoms in our study watershed net sedimentation rate sedimentation less erosion averaged over valley bottom area is 2 6 mm y a value that is similar to independent direct measurements of sedimentation and erosion in a nearby watershed evaluation of the relative contributions to sediment mass balance of upland supply valley bottom sedimentation and erosion and watershed delivery indicates that if valley bottom rates of sedimentation exceed erosion as indicated by recent studies then the proportion of watershed sediment delivery derived from stream banks is necessarily small although sediment yield estimated from stream gage records is similar in magnitude to that from ponds for watersheds smaller than 20 km 2 sediment yield from reservoir sedimentation is a factor of five larger than that estimated from gage records for watersheds larger than 140 km 2 this observation confirms that the different methods provide very different estimates of sediment yield this possibility is reinforced by a sediment yield of 14 mg km 2 y from a gage immediately above a reservoir with a yield of 142 mg km 2 y based on reservoir accumulation

calcareous nannoplankton from the boreal late albian of nw germany kirchrode i borehole its biostratigraphy and cyclicity abstract one hundred and sixty samples from the continuously cored kirchrode i research borehole were examined for calcareous nannoplankton a total of 106 coccolith taxa were identified the state of preservation varied from poor to good mostly moderately good the coccolith assemblages were assigned to the eiffellithus turriseiffelii zone cc9 and prediscosphaera columnata zone cc8 of the upper albian sissingh geol en mijnb 56 1977 37 a count of the taxa was made at 5 m intervals and in certain sections at 1 m intervals this study focuses on the dating of the sequence with calcareous nannofossils and the determination of the fluctuations in the abundance of calcareous nannofossils the cyclicity found in the changes in their abundance was correlated with cycles determined for the changes in the calcium carbonate content of the sediment

climatic and oceanographic isotopic signals from the carbonate rock record and their preservation stable isotopic data from marine limestones and their constituent fossils and marine cements can provide quantitative evidence for changes in global climate and ocean circulation oxygen isotopic data can indicate changes in temperature and ocean composition whereas stratigraphic variation in carbon isotope ratios may reflect changes in the carbon cycle that can be linked to changes in oceanic productivity and atmospheric greenhouse gases terrestrial carbonates meteoric cements calcretes and speleothems similarly offer significant potential for understanding the evolution of terrestrial climates by providing evidence for the composition of rainwater and the nature of vegetative cover primary environmental isotopic signals may be obscured by the effects of post depositional diagenetic alteration cementation and replacement reactions can take place in a wide range of diagenetic environments the diagenetic history of an individual limestone is determined by a combination of its mineralogical diagenetic potential and depositional setting together with subsequent changes in relative sea level and burial history carbon isotopic values are less prone to alteration during diagenesis than oxygen values but shifts can be significant where organogenic carbon is incorporated linear covariation of carbon and oxygen values is not a reliable indicator of diagenetic alteration water rock interaction and fluid mixing may produce non linear distributions attempts to determine long term changes in climatic and oceanographie conditions through isotope stratigraphy of shallow water limestones must include an assessment of the diagenetic history of the materials analysed petrographic examination using conventional microscopy backed up where appropriate by cathodoluminescence and scanning electron microscopy together with elemental and strontium isotopic analysis can help to identify the effects of diagenetic alteration where material with a range of different degrees of alteration is preserved in the same sediment it may be possible to compare patterns of isotopic and elemental variation and to attempt to unravel the effects of diagenesis in order to determine primary environmental isotopic signals recent research has shown that these techniques can be successfully employed in both phanerozoic and precambrian sediments

legacy sediment storage in new england river valleys anthropogenic processes in a postglacial landscape abstract legacy sediment associated with erosion from land clearing is a common feature in river valleys of the unglaciated mid atlantic piedmont region here we quantify the volume of legacy sediment storage in three watersheds in new england a formerly glaciated region with similar history and intensity of forest clearing and milldam construction during the seventeenth to nineteenth centuries we combine field observations of bank stratigraphy radiocarbon dating and mapping of terraces and floodplains using lidar digital elevation models and other gis datasets the 68 km2 south river watershed in western massachusetts exhibits the most extensive evidence for legacy sediment storage we visited 18 historic dam sites in the watershed and found field evidence for up to 2 2 m of fine sand and silt legacy sediment storage at 14 of the sites in the 555 km2 sheepscot river watershed in coastal maine we visited 13 historic dam sites and found likely legacy sediment up to 2 3 m thick at six of the dams in the 171 km2 upper charles river watershed in eastern massachusetts we investigated 14 dam sites and found legacy sediment up to 1 8 m thick at two of them stratigraphically we identified the base of fine grained legacy sediment from a change to much coarser grain size gravel at most sites or to glacial lacustrine or marine deposits along the sheepscot river we observed cut timbers underlying historic sediment at several locations likely associated with sawmill activities only at the charles river were we able to radiocarbon date the underlying gravel layer 1281 1391 calibrated ce at no site did we find a buried organic rich holocene soil in contrast to the field relations commonly observed in the mid atlantic region we use lidar elevation data to map planar terrace extents in each watershed estimate thickness of remaining legacy sediment found stored behind breached or removed milldams and estimate volumes of remaining legacy sediment storage in valley bottoms for entire watersheds the maximum volume of stored legacy sediment estimated for the south sheepscot and upper charles watersheds is 2 5 106 m3 3 7 106 m3 and 2 6 104 m3 respectively these volumes of legacy sediment can be translated to an equivalent thickness of soil eroded from each watershed 37 mm 7 mm and 0 2 mm respectively we attribute the variation in presence and thickness of legacy sediment at the new england sites to the existence or absence of upstream sediment supply in the form of thick glacial deposits and to sinks such as lakes and wetlands along valley bottoms of the three study watersheds the south river has the most extensive glacial sediments fewest sinks and the most legacy sediment in storage along the river corridor

biochemostratigraphy of an upper albian turonian succession from the southeastern neo tethys margin sw iran abstract a neo tethyan upper albian turonian hemi pelagic carbonate succession sarvak formation accessible in outcrop in the zagros sw iran was investigated using sedimentology microfacies analysis planktonic foraminifera biostratigraphy and carbon isotope stratigraphy the succession contains six biozones including thalmanninella th appenninica th globotruncanoides rotalipora cushmani whiteinella archaeocretacea helvetoglobotruncana helvetica and marginotruncana schneegansi some of these biozones show variable stratigraphic positions throughout the tethyan and boreal realms that hinder correlation of the studied iranian section with european reference sections therefore the correlation of the existing biostratigraphic framework was complemented by carbonate carbon isotope stratigraphy based on bulk carbonate material despite the low resolution of the presented carbon isotope record pronounced global events including the late turonian events cenomanian turonian boundary ctb event oae 2 and albian cenomanian boundary acb event can be distinguished the 13c excursions provide global synchronous time lines for correlation the distinguished biozones were compared among the sections regarding their stratigraphic positions relative to these time lines the correlation tentatively suggests that the biostratigraphic datum marking the acb is diachronous with an se nw trend first appearance datum fad of th appenninica varies from the upper albian to the lower cenomanian the fad of th globotruncanoides is also variable from the upper albian to the lower cenomanian however the middle cenomanian turonian biozones including rotalipora cushmani and whiteinella archaeocretacea zones are synchronous elevated pco2 contributed to the gradual increase of the sst sea surface temperature during the cenomanian and the dramatic climax at the earliest turonian this trend closely correlates with the change from the diachronous acb biozones to synchronous ctb biozones possibly increasing ssts provided temperature tolerance range for the species throughout different latitudes and assisted their rapid distribution moreover the warming raised the sea level from the latest albian to turonian that inundated landbridges resulting in an enhanced marine circulation and faster distribution of planktonic species throughout the neo tethys ocean

legacy sediments and historic land use chemostratigraphic evidence for excess nutrient and heavy metal sources and remobilization major and trace element geochemistry of sediment cores of legacy deposits i e sediments eroded from upland areas starting in colonial times reflecting intensive land use that have altered pre colonial environments and are impairing modern environments from behind former mill dams in different land use sub watersheds of the yellow breeches creek cumberland county pennsylvania usa provide insight into the origins of elements with multiple natural and anthropogenic sources in comparing a forested land use watershed with an agriculturally affected one we find similar elemental ratios with al for pre settlement and early legacy sediments but increasing trends of nutrient elements and select trace metals through time in the agriculturally affected legacy deposit likely sources of excess p cu and pb over background are fertilizer pesticides and other soil amendments pb trends show smaller increases over time in the forested land use subwatershed mostly due to the input of leaded gasoline emissions to the atmosphere and ubiquitous fallout to all watersheds the agriculturally affected subwatershed cores show significantly more pb suggesting multiple sources the continued remobilization of legacy sediments from thousands of mill ponds in the eastern united states suggests that this source of nutrients and trace elements may add significantly to the degradation of downstream ecosystems such as the chesapeake bay

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

late albian paleoceanography of the western subtropical north atlantic a late albian early cenomanian record 103 3 to 99 0 ma including organic rich deposits and a 13c increase associated with oceanic anoxic event 1d oae 1d is described from ocean drilling program sites 1050 and 1052 in the subtropical atlantic foraminifera are well preserved at these sites paleotemperatures estimated from benthic 18o values average 14 c for middle bathyal site 1050 and 17 c for upper bathyal site 1052 whereas surface temperatures are estimated to have ranged from 26 c to 31 c at both sites among planktonic foraminifera there is a steady balance of speciation and extinction with no discrete time of major faunal turnover oae 1d is recognized on the basis of a 1 2 13c increase 100 0 99 6 ma which is similar in age and magnitude to 13c excursions documented in the north atlantic and western tethys organic rich black shales are present throughout the studied interval at both sites however deposition of individual black shale beds was not synchronous between sites and most of the black shale was deposited before the oae 1d 13c increase a similar pattern is observed at the other sites where oae 1d has been recognized indicating that the site s of excess organic carbon burial that could have caused the 13c increase has have yet to be found our findings add weight to the view that oaes should be chemostratigraphically 13c rather than lithostratigraphically defined

foraminiferal response to mid cenomanian upper cretaceous palaeoceanographic events in the anglo paris basin northwest europe we have analysed the sedimentology macrofossil event horizons including pulse faunas and foraminiferal succession 80 samples from an 8 m succession in the upper lower and lower middle cenomanian upper cretaceous at folkestone southeast england comparative sedimentological analysis of successions in southern and northeastern england indicates the presence of three hierarchies of cycle 20 kyr productivity chalk marl couplets cycles attributed to the milankovitch precession cycle 100 kyr sea level cycles attributed to the milankovitch eccentricity cycle and l myr cycles attributed to longer term sea level cycles previously recognised macrofossil pulse faunas occur preferentially at the bases of the 100 kyr eccentricity cycles we analysed the foraminiferal fauna across the lower middle cenomanian boundary at abbott s cliff folkestone in great detail 80 samples in 8 m the foraminiferal succession is also intricately related to the 1 myr sea level and 100 kyr eccentricity cycles changes related to the long term cycles include variations in the abundance of the benthic foraminifera tritaxia gyroidinoides lingulogavelinella and dorothia and an increase in benthic diversity in the transgressive deposits changes related to the 100 kyr eccentricity cycles include the presence of rotalipora ex gr reicheli in the lower part and rarely upper part of cycles the abundance of planktics both absolute and relative in the middle to upper part of cycles an increase in the proportion of gavelinella berthelini and g reussi in the upper part of cycles we present a stratified water column model to explain the changes related to the 100 kyr scale cycle 1998 elsevier science b v

reconstruction of short term palaeoceanographic changes during the formation of the late albian niveau breistroffer black shales oceanic anoxic event 1d se france the niveau breistroffer black shale succession in the vocontian basin se france is the regional equivalent of the widely distributed late albian oceanic anoxic event 1d the studied black shale rich interval at the col de palluel section is 6 28 m thick and comprises four black shale units with up to 2 5 wt total organic carbon toc intercalated with marlstones calcareous nannofossil palynomorph planktic foraminifera and stable isotopic data from the niveau breistroffer succession suggest that short term climate changes influenced its deposition with relatively warm and humid climate during black shale formation in comparison with relatively cool and dry climatic conditions during marlstone deposition an increase in the terrigenous marine ratio of palynomorphs indicates enhanced humidity and higher runoff during black shale formation a nutrient index based on calcareous nannofossils and the abundance pattern of small 63 125 m hedbergellid foraminifera show short term changes in the productivity of the surface water surface water productivity was reduced during black shale formation and increased during marlstone deposition a calcareous nannofossil temperature index and bulk rock oxygen isotope data indicate relative temperature changes with warmer surface waters for black shale samples at these times warm humid climate and reduced surface water productivity were accompanied by greater abundances of subsurface dwelling calcareous nannofossils nannoconids and planktic foraminifera rotaliporids these taxa presumably indicate more stratified surface water conditions we suggest that the formation of the niveau breistroffer black shales occurred during orbitally induced increase in monsoonal activity that led to increasing humidity during periods of black shale formation this in turn caused a decrease in low latitude deep water formation and probably an increase in surface water stratification the combination of these two mechanisms caused depleted o 2 concentrations in the bottom water that increased the preservation potential of organic matter

erosion of the eastern united states observed with 10be the problem of identifying areas of accelerated erosion in a dynamic landscape is complicated the limited history of sediment yield measurements makes this task difficult even if geomorphic evidence is available beryllium 10 a cosmogenic isotope produced by cosmic rays interacting with the earth s atmosphere and surface has chemical and physical properties that make it useful as a tracer for erosion and sediment transport processes the rarity of the stable isotope 9be allows 10be to be detected with accelerator mass spectrometry in natural materials at extremely low levels backgrounds for rocks and sediments below 105 atom per g are now attainable a value to be compared with an average deposition rate of 1 3 106 atom cm 2 yr 1 the affinity of be for the components of soil and sediment is sufficiently high that it is effectively immobilized on contact thereby allowing 10be to function as a tracer of sediment transport to a good approximation all the 10be transport out of a drainage basin is on the sediment leaving it the number of 10be atoms passing the gauging station can be determined by measuring the concentration of the isotope in the sediment if the annual sediment load is known the ratio of the 10be carried from the basin by the sediment to that incident upon it called the erosion index has been determined for 48 drainage basins within the same physiographic province which allows them to be reasonably compared all of which have sediment yield data basins located in the atlantic coastal plain have an average index of 0 3 with the maximum observed being 0 9 basins located between the fall line and the mountains a region called the piedmont have an average value of 2 2 with individual values ranging from 0 6 to 6 7 this marked difference is thought to result from two centuries of farming on land of moderate gradient basins in the highland regions reflect local conditions with low indices for those in grass and timber and high indices associated with destructive land use the data allow an estimate of the erosion index for the pre colonial piedmont which then allows the pre colonial sediment yield to be calculated a number of basins have also been examined world wide with similar conclusions derived an important deviation from the rule is noted for rivers that erode large regions of loess such as the mississippi hwang ho and yangtze large aeolian deposits were laid down during the ice age in these basins deposits that brought inherited 10be with them and that are easily eroded

carbon isotope stratigraphy of early cretaceous urgonian shoal water deposits diachronous changes in carbonate platform production in the north western tethys abstract carbonate platforms are highly sensitive ecological systems that typically show rapid and characteristic response modes to environmental and climatic changes acting both on a regional scale and global scale a widely accepted hypothesis proposes that the late barremian stepwise establishment of the urgonian carbonate platform on the northern tethyan shelf was related to a gradual change from predominantly humid towards more arid greenhouse conditions this climate change resulted in the reorganisation of the carbonate platform ecosystem from heterozoan towards photozoan dominated assemblages and a decrease of organic matter burial in tethyan and boreal basins in order to decipher the palaeoenvironmental and climatic boundary conditions of these major changes in neritic and pelagic settings a precise chronostratigraphy of urgonian carbonate platform evolution is needed here we provide an integrated stratigraphic framework of lower barremian to lower aptian urgonian carbonate platform sections cluses forclaz located at the northern rim of the tethys subalpine chains ese france with special focus on sedimentological analyses and high resolution carbon isotope stratigraphy a characteristic barremian aptian carbon isotope pattern permits precise platform to basin correlation with cyclostratigraphic and ammonite dated pelagic and hemipelagic tethyan sections in the vocontian trough angles combe lambert glaise and umbria marche basin gorgo a cerbara similar to helvetic shoal water settings the carbonate platform in the subalpine chains experienced a gradual transition from heterozoan to photozoan dominated ecosystems this biogenic pattern points to a gradual change of the carbonate platform after the so called early barremian crisis towards an oligotrophic rimmed platform system urgonian limestone formation according to the chronostratigraphy of urgonian carbonate platform evolution in the subalpine chains established here the installation of a photozoan dominated rudist rich platform ecosystem referred to as urgonian limestones sensu stricto occurred at the early late barremian transition the onset of changes in the carbonate production mode heterozoan versus mixed heterozoan photozoan versus photozoan clearly predates the onset of similar lithological changes in the helvetic realm by about 1 0 to 1 2 myr the established chronostratigraphic framework points to a link between the change towards photozoan dominated limestones and fading palaeoenvironmental perturbations related to the mid barremian event which is associated with major faunal turnovers and the onset of cyclic black shale deposition in the central tethyan realm judging from palaeoenvironmental proxies including kaolinite phosphorus and black marl limestone ratios oscillating predominantly humid and relatively arid greenhouse conditions modulated the observed pattern in urgonian carbonate platform production mode and the varying frequencies of black shale deposits in the tethyan and boreal realms transient blooms of the orbitolinid foraminifera palorbitolina lenticularis at the onset of a marked upper barremian positive carbon isotope shift are interpreted to reflect increasing nutrient influx most probably related to accelerated hydrological cycling and or sea level rise these strata do not represent an over regional correlatable lithostratigraphic unit but likely an expression of progressive northern tethyan environmental and oceanographic change possibly related to ontong java large igneous province volcanism in the prelude of oceanic anoxic event 1a oae

bedload transport over run of river dams delaware u s a abstract we document the detailed morphology and bed sediment size distribution of a stream channel upstream and downstream of a 200 year old run of river dam on the red clay creek a fifth order stream in the piedmont of northern delaware and combine these data with hec ras modeling and bedload transport computations we hypothesize that coarse bed material can be carried through run of river impoundments before they completely fill with sediment and we explore mechanisms to facilitate this transport only 25 of the accommodation space in our study site is filled with sediment and maximum water depths are approximately equal to the dam height all grain size fractions present upstream of the impoundment are also present throughout the impoundment a characteristic coarse grained sloping ramp leads from the floor of the impoundment to the crest of the dam a 2 3 m deep plunge pool has been excavated below the dam followed immediately downstream by a mid channel bar composed of coarse bed material similar in size distribution to the bed material of the impoundment the mid channel bar stores 1472 m3 of sediment exceeding the volume excavated from the plunge pool by a factor of 2 8 these field observations are typical of five other sites nearby and suggest that all bed material grain size fractions supplied from upstream can be transported through the impoundment up the sloping ramp and over the top of the dam sediment transport computations suggest that all grain sizes are in transport upstream and within the impoundment at all discharges with return periods from 1 to 50 years our computations suggest that transport of coarse bed material through the impoundment is facilitated by its smooth sandy bed model results suggest that the impoundment is currently aggrading at 0 26 m year but bed elevations may be recovering after recent scour from a series of large floods during water year 2011 2012 we propose that impoundments upstream of these run of river dams behave as long pools that adjust their bed elevation and texture to transport the load supplied by the watershed rather than as impounded reservoirs with little bed material transport capacity scour may only occur during episodic high flows followed by aggradation during periods of low flow

black shales and carbon isotopes in pelagic sediments from the tethyan lower jurassic detailed sampling and analysis of jurassic pelagic limestones and marls from italy hungary and switzerland have enabled construction of an isotope stratigraphy across the pliensbachian toarcian boundary with resolution to the zonal level the oxygen isotope record is unremarkable the carbon isotopes however show two positive excursions one relatively minor during the pliensbachian margaritatus zone subnodosus subzone the other more major during the toarcian early falciferum zone where a maximum 13c value of 4 52 pdb is attained these intervals are known to be favoured periods of organic rich sedimentation in diverse parts of the globe and the isotopic excursions are interpreted as a response to abnormally high rates of storage of organic carbon in the sedimentary record a comparable phenomenon has been documented from the cenomanian turonian boundary in the cretaceous where it has been referred to the influence of an oceanic anoxic event some italian sections spanning this lower jurassic interval contain organic rich shales in the falciferum zone the isotopic signatures from their included locally manganiferous carbonate betray a considerable diagenetic overprint and they cannot therefore be incorporated in a composite isotopic curve carbon isotopes from the organic carbon itself are extremely negative falling to 33 pdb and in one section examined in detail correlate with the calcium carbonate content of the shales they may reflect a partial change to a non calcified planktonic biota during deposition of this lime poor interval possibly responding to upwelling and increased fertility of near surface waters the onset of upwelling may have been as early as spinatum tenuicostatum zone time that is at the pliensbachian toarcian boundary

secular variation in late cretaceous carbon isotopes a new δ13c carbonate reference curve for the cenomanian campanian 99 6 70 6 ma carbon stable isotope variation through the cenomanian santonian stages is characterized using data for 1769 bulk pelagic carbonate samples collected from seven chalk successions in england the sections show consistent stratigraphic trends and 13c values that provide a basis for highresolution correlation positive and negative 13cexcursions and inflection points on the isotope profiles are used to define 72 isotope events key markers are provided by positive 13c excursions of up to 2 the albian cenomanianboundary event mid cenomanian event i thecenomanian turonian boundary event the bridgewick hitch wood and navigation events of late turonian age and the santonian campanian boundary event isotope events are isochronous within a framework provided by macrofossil datum levels and bentonite horizons an age calibrated composite 13c reference curve and an isotope event stratigraphy are constructed using data from the english chalk the isotope stratigraphy is applied to successions in germany france spain and italy correlation with pelagic sections at gubbio central italy demonstrates general agreement between biostratigraphic and chemostratigraphic criteria in the cenomanian turonian stages confirming established relationships between tethyan planktonic foraminiferal and boreal macrofossil biozonations correlation of the coniacian santonian stages is less clear cut magnetostratigraphic evidence for placing the base of chron 33r near the base of the upper santonian is in good agreement with the carbon isotope correlation but generates significant anomalies regarding the placement of the santonian and campanian stage boundaries with respect to tethyan planktonic foraminiferal and nannofossil zones isotope stratigraphy offers a more reliable criterion for detailed correlation of cenomanian santonian strata than biostratigraphy with the addition of campanian 13c data from one of the english sections a composite cenomanian campanian age calibrated reference curve is presented that can be utilized in future chemostratigraphic studies the cenomanian campanian carbon isotope curve is remarkably similar in shape to supposedly eustatic sea level curves increasing 13c values accompanying sea level rise associated with transgression and falling 13c values characterizing sea level fall and regression the correlation between carbon isotopes and sea level is explained by variations in epicontinental sea area affecting organic matter burial fluxes increasing shallow sea floor area and increased accommodation space accompanying sea level rise allowedmore efficient burial ofmarine organic matter with the preferential removal of 12c from the marine carbon reservoir during sea level fall reduced seafloor area marine erosion of previously deposited sediments and exposure of basin margins led to reduced organiccarbon burial fluxes and oxidation of previously deposited organic matter causing falling 13c values additionally drowning of carbonate platforms during periods of rapid sea level rise may have reduced the global inorganic relative to the organic carbon flux further enhancing 13c values while renewed platform growth during late transgressions and highstands prompted increased carbonate deposition variations in nutrient supply changing rates of oceanic turnover and the sequestration or liberation of methane from gas hydrates may also have played a role in controlling carbon isotope ratios

recent and historic sediment dynamics along difficult run a suburban virginia piedmont stream abstract suspended sediment is one of the major concerns regarding the quality of water entering the chesapeake bay some of the highest suspended sediment concentrations occur on piedmont streams including difficult run a tributary of the potomac river draining urban and suburban parts of northern virginia accurate information on catchment level sediment budgets is rare and difficult to determine further the sediment trapping portion of sediment budget represents an important ecosystem service that profoundly affects downstream water quality our objectives with special reference to human alterations to the landscape include the documentation and estimation of floodplain sediment trapping present and historic and bank erosion along an urbanized piedmont stream the construction of a preliminary sediment balance and the estimation of legacy sediment and recent development impacts we used white feldspar markers to measure floodplain sedimentation rates and steel pins to measure erosion rates on floodplains and banks respectively additional data were collected for from legacy sediment thickness and characteristics mill pond impacts stream gaging station records topographic surveying and sediment density texture and organic content data were analyzed using gis and various statistical programs results are interpreted relative to stream equilibrium affected by both post colonial bottomland sedimentation legacy and modern watershed hardening associated with urbanization six floodplain channel sites from high to low in the watershed were selected for intensive study bank erosion ranges from 0 to 470 kg m y and floodplain sedimentation ranges from 18 to 1369 kg m y m refers to meters of stream reach upstream reaches are net erosional while downstream reaches have a distinctly net depositional flux providing a watershed sediment balance of 2184 kg m y trapped within the system the amounts of both deposition and erosion are large and suggest nonequilibrium channel conditions both peak discharge and number of peaks above base have substantially increased since the mid 1960s when urbanization of the watershed began deposition patterns are most closely correlated with channel gradient sinuosity and channel width floodplain width for recent and historic periods the substantial amounts of fine grained sediment deposited on the floodplain over the past two centuries or so do not appear to be closely related to historic mill pond presence or location the floodplain continues to provide the critical ecosystem service of sediment trapping in the face of multiple human alterations trends in sediment deposition erosion may react rapidly to land use practices within the watershed and offer a valuable barometer of the effects of management actions

blake nose stable isotopic evidence against the mid cenomanian glaciation hypothesis detailed multitaxon stable isotope 18 o and 13 c data from blake nose western north atlantic argue against a mid cenomanian glaciation event during the mid cretaceous greenhouse results generated are precisely correlated to sea level changes inferred from european sequence stratigraphy using the twin 13 c excursions mid cenomanian event mce ia and mce ib microfossils analyzed surface dwelling to deep dwelling planktonic foraminifera benthic foraminifera coccoliths show remarkably consistent intertaxon 18 o and 13 c offsets comparative scanning electron microscope and sr ca analyses allow some 18 o data to be eliminated because of selective diagenesis across mce ia the proposed interval of major glacioeustatic regression the planktonic 18 o values are constant for each taxon the absence of a mean seawater 18 o shift contradicts predictions for the mid cenomanian glaciation episode the benthic 18 o records show significant fluctuations during mce i implying short term variability in north atlantic intermediate water and deep water circulation patterns and or sources at that time

major and trace element characterization of oceanic anoxic event 1d oae 1d insight from the umbria marche basin central italy abstract the pialli level in the umbria marche basin central italy correlates with the lowermost part of the positive carbon isotopic excursion characterizing the late albian early cenomanian oceanic anoxic event 1d oae 1d high resolution litho bio and chemostratigraphic data from the monte petrano and le brecce sections allow for a bed by bed comparison of the two successions and discriminate local from basin scale signals we present new x ray fluorescence icp ms and toc data for both the limestones and the pialli level shales integrated with available carbonate carbon isotopes and nannofossil temperature and nutrient indices data indicate a homogenous background sedimentation dominated by pelagic carbonates biogenic silica with little contribution by clays the limited variation in lithogenic elements points to an essentially homogeneous detrital source area with limited fluvial terrigenous input higher mn concentrations coupled with low enrichments in redox sensitive elements such as u fe s re mo ag suggest that the pialli level shales represent temporary suboxia without reaching anoxia furthermore p authigenic ba cd and ni enrichments together with nannofossil nutrient index indicate generally low primary productivity conditions along the entire succession with only minor increases for some of the black to dark grey shales of the pialli level the nannofossil temperature index highlights a warm climate during the oae 1d with the warmest conditions experienced during the deposition of the pialli level shales during the late albian the warm and humid climate was interrupted by brief episodes of relatively warmer and less saline surface waters ensuring slower rates of bottom water renewal and producing temporary suboxic conditions such paleoceanographic dynamics would be the continuation of episodic warmer and humid pulses characterizing the late albian interval in the umbria marche basin as such the pialli level can be considered the result of a last episode closing a cycle before the establishment of a steadier climate during the early cenomanian

the potential impact of green agendas on historic river landscapes numerical modelling of multiple weir removal in the derwent valley mills world heritage site uk the exploitation of river systems for power and navigation has commonly been achieved through the installation of a variety of in channel obstacles of which weirs in britain are amongst the most common in the uk the historic value of many of these features is recognised by planning designations and protection more commonly associated with historic buildings and other major monuments their construction particularly in the north and west of britain has often been associated with industries such as textiles chemicals and mining which have polluted waterways with heavy metals and other contaminants the construction of weirs altered local channel gradients resulting in sedimentation upstream with the potential as well for elevated levels of contamination in sediments deposited there for centuries these weirs have remained largely undisturbed but as a result of the growth in hydropower and the drive to improve water quality under the european union s water framework directive these structures are under increasing pressure to be modified or removed altogether at present weir modifications appear to be considered largely on an individual basis with little focus on the wider impacts this might have on valley floor environments using a numerical modelling approach this paper simulates the removal of major weirs along a 24 km stretch of the river derwent derbyshire uk designated as a unesco world heritage site the results suggest that although removal would not result in significant changes to the valley morphology localised erosion would occur upstream of structures as the river readjusts its base level to new boundary conditions modelling indicates that sediment would also be evacuated away from the study area in the context of the derwent valley this raises the potential for the remobilisation of contaminants legacy sediments within the wider floodplain system which could have detrimental long term health and environmental implications for the river system worldwide rivers have a common association with industry being the focus of settlement and development since the earliest civilisations with channel engineering a common practice therefore the conceptual issues raised by this study have global resonance and are particularly important where heritage protection is less robust and structures can be removed with little consideration of the environmental consequences