late cenomanian to middle turonian high resolution carbon isotope stratigraphy new data from the munsterland cretaceous basin germany abstract new high resolution carbon isotope stratigraphies from two basinal pelagic carbonate successions in northern germany halle and oerlinghausen munsterland cretaceous basin resolve late cenomanian to early mid turonian carbon cycle variations at timescales of less than 100 kyr beside the major carbon isotope excursion of the late cenomanian oceanic anoxic event oae 2 11 small scale distinct features are precisely resolved in the 13c carbonate curve and related to boreal macrofossil zonations the small scale carbon isotope events correspond to secular 13c carbonate variations identified previously in the english chalk the boreal high resolution 13c carbonate curve shows a detailed coincidence with two tethyan 13c curves from italy what demonstrates the interregional significance of the 13c dates and allows their correlation within error limits of 40 kyr furthermore the new 13c curve enables the calibration of boreal and tethyan macro and microfossil zonations accordingly the tethyan calcareous nannoplankton boundary nc13 nc14 corresponds to the boreal fo of c woollgari the index taxon for the lower middle turonian boundary the cyclic appearance and the temporal spacing of the small scale carbon isotope events suggest that orbital forcing exerted control on surface water productivity and organic matter preservation at the sea floor

eustatic sea level record for the cenomanian late cretaceous extension to the western interior basin usa a combination of biostratigraphic markers ammonites inoceramid bivalves and carbon isotope excursions is employed to establish a high resolution correlation between the middle to late cenomanian successions of the western interior basin usa and the anglo paris basin southern uk sequences identified from sedimentologic criteria in the pueblo succession and elsewhere in the western interior basin are shown to coincide precisely with globally recognized sea level events and were therefore under eustatic control this evidence refutes arguments that cenomanian sequences in the western interior basin were formed by local tectonic events the interaction of longer term tectonic movements and more rapid eustatic change may have simply enhanced the amount of erosion associated with sequence boundaries a crossplot of radiometric ages derived from north american bentonites against an orbitally tuned time scale developed in the anglo paris basin provides support for the argument that the sequences were controlled by the 405 k y long eccentricity cycle

an example of alternative correlation techniques in a low accommodation setting nonmarine hydrocarbon system the lower cretaceous mannville basal quartz succession of southern alberta chemostratigraphy and heavy mineral techniques have been applied to the lower cretaceous basal quartz in the western canada sedimentary basin the aim of the study is to demonstrate that these two techniques can be used to help understand the complex stratigraphy of reservoirs deposited in low accommodation fluvial settings the basal quartz is an ideal unit to demonstrate their applicability in stratigraphic studies of hydrocarbon reservoirs because extensive mapping and petrographic studies have enabled the establishment of a rigorous stratigraphic framework despite its complexity resulting from deposition in a low accommodation fluvial setting the three component units analyzed in the basal quartz horsefly unit bantry alderson taber bat unit and ellerslie unit each have unique geochemical and heavy mineral characteristics chemostratigraphic analysis shows that silty claystones from the horsefly bat and ellerslie units have distinctly different geochemistry from one another with the variations being caused by changes in clay mineralogy and other components such as feldspar apatite and zircon the geochemistry also suggests periodic volcanogenic input influenced the silty claystones of the basal quartz heavy mineral analysis shows that sandstones from the three units can be distinguished on the basis of ratio parameters such as apatite tourmaline rutile zircon and zircon tourmaline which are controlled by differences in provenance and intensity of weathering during transport

the cenomanian turonian oceanic anoxic event in the south atlantic new insights from a geochemical study of dsdp site 530a abstract one of the key objectives of deep sea drilling project dsdp leg 75 was to shed light on the underlying causes of cretaceous oceanic anoxia in the south atlantic by addressing two major hypotheses productivity productivity driven anoxia vs enhanced ocean stratification leading to preservation of organic matter and black shale deposition here we present a detailed geochemical dataset from sediments deposited during the cenomanian turonian c t transition and the global oceanic anoxic event 2 oae 2 at dsdp site 530a located off shore namibia southeast angola basin north of walvis ridge to characterise the succession of alternating black and green shales at this site and to reconstruct the evolution of their paleoenvironmental setting we have combined data derived from investigations on bulk organic matter biomarkers and the inorganic fraction the location of the c t boundary itself is biostratigraphically not well constrained due to the carbonate poor but organic matter rich facies of these sediments the bulk 13corg record and compound specific 13c data in combination with published as well as new biostratigraphic data enabled us to locate more precisely the c t boundary at dsdp site 530a the compound specific 13c record is the first of this kind reported from c t black shales in the south atlantic it is employed for paleoenvironmental reconstructions and chemostratigraphic correlation to other c t sections in order to discuss the paleoceanographic aspects and implications of the observations at dsdp site 530a in a broader context e g with regard to the potential trigger mechanisms of oae 2 global changes in black shale deposition and climate on a stratigraphic level an approximation and monitoring of the syndepositional degree of oxygen depletion within the sediments bottom waters in comparison to the upper water column is achieved by comparing normalised concentrations of redox sensitive trace elements with the abundance of highly source specific molecular compounds these biomarkers are derived from photoautotrophic and simultaneously anoxygenic green sulphur bacteria chlorobiacea and are interpreted as paleoindicators for events of photic zone euxinia in contrast to a number of other oae 2 sections that are characterised by continuous black shale sequences dsdp site 530a represents a highly dynamic setting where newly deposited black shales were repeatedly exposed to conditions of subtle bottom water re oxidation presumably leading to their progressive alteration into green shales the frequent alternation between both facies and the related anoxic to slight oxygenated conditions can be best explained by variations in vertical extent of an oxygen minimum zone in response to changes in a highly productive western continental margin setting driven by upwelling

chemostratigraphy a method to improve interwell correlation in barren sequences a case study using onshore duckmantian stephanian sequences west midlands u k abstract chemostratigraphy has been applied to onshore duckmantian stephanian successions encountered in outcrop and penetrated by two boreholes from the west midlands u k these successions represent the onshore equivalents of the barren red measures which are important hydrocarbon bearing sequences in the southern north sea much is known about the onshore successions in terms of sedimentology mineralogy and provenance and thus they provide the ideal test for the validity of chemostratigraphy as a stratigraphic tool reliable inorganic geochemical data have been acquired from geochemical analyses of core sidewall core and cuttings samples with 19 elements being determined stratigraphic variations in elemental concentrations are compared with known variations in the mineralogical data the established lithostratigraphic units of the duckmantian stephanian intervals can also be recognized from the geochemical data and by using these data can be subdivided further this results in an independent chemostratigraphic correlation being established for the two boreholes which has been assessed statistically by discriminant function analysis from the geochemical and mineralogical data distinct changes in provenance are identified within the upper carboniferous successions the sediments of the coal measures were derived from a north westerly and westerly source caledonian whereas the etruria formation sediments came from the wales brabant massif the sediments having mixed caledonian and cadomian characteristics eventually these sediments were replaced by sediments from a southern hercynian source halesowen and salop formations

identifying and removing noise from the monterey ocean bottom broadband seismic station mobb data when compared to quiet land stations the very broadband monterey ocean bottom seismic station mobb shows increased long period background as well as signal generated noise both sources of noise are unavoidable in shallow ocean bottom installations and postprocessing is required to remove them from seismic observations the long period background noise observed for periods longer than 20 s is mainly due to infragravity waves and ocean currents the shorter period signal generated noise on the other hand is due to reverberations of the seismic waves in the shallow sedimentary layers as well as in the water layer we first present the steps that were taken prior to and during the instrument deployment to minimize instrument generated noise as well as to avoid noise due to water flow around the instrument we then present results from two postprocessing methods that can be used to remove the long period background noise which both utilize the ocean bottom pressure signal locally recorded on a differential pressure gauge dpg one consists of subtracting the locally recorded ocean bottom pressure from the vertical seismic acceleration signal in this case the frequency independent scale factor is linearly estimated from the data the other one makes use of the transfer function between the vertical seismic and pressure signal to predict the vertical component deformation signal the predicted signal is then removed from the vertical seismic data in either frequency or time domain we also present two methods that can be used to remove the signal generated noise one employs the empirical transfer function constructed from mobb data and nearby land station data that do not show the signal generated noise the other one uses a synthetic transfer function computed by modeling the response of shallow layers at the mobb location using either of the two transfer functions most of the signal generated noise can be removed from the mobb data by deconvolution

magnetostratigraphy susceptibility of the přidolian lochkovian silurian devonian gssp klonk czech republic and a coeval sequence in anti atlas morocco abstract the magnetosusceptibility event and cyclostratigraphy msec record for the p idolian lochkovian silurian devonian global boundary stratotype section and point gssp klonk prague basin czech republic is described and used to establish a magnetostratigraphy susceptibility profile for the gssp gssp msec data are summarized into three magnetozones msz the tma msz late p idolian with 13 msszs mssz the klonk msz latest p idolian and earliest lochkovian with 17 msszs and the voskop msz early lochkovian with 7 msszs the base of klonk mssz 2 is coincident with the base of lochkovian and the devonian the proposed magnetostratotype for the p idolian lochkovian boundary is supported by ms data from a nearby core through the gssp sequence and into the upper ludlow three additional mszs are recognized for the portion of the core sequence older than the gssp boundary sequence the extension of the mszs and msszs away from the proposed magnetostratotype is tested by comparison with a lochkovian sequence in the western sahara of southeastern morocco mszs are the result of global sea level fluctuations that alter base level and the pattern of erosion and influx of detrital paramagnetic mineral components into the marine environment large scale transgressive and regressive patterns interpreted from the msec data establish that the silurian devonian boundary in the barrandian region falls between a short lived transgressive pulse in the latest p idolian and an equally short lived regressive pulse in the earliest lochkovian msszs identified in the gssp and core sequences are the result of variation in climate cycles and the resulting periodicity can explained by either the 38 9 ka silurian and devonian equivalent of the modern 54 ka obliquity cycle or the eccentricity cycle of 106 ka periodicity use of the obliquity periodicity gives a duration for the barrandian lochkovian of 4 46 ma which agrees with the most recent geochronometric estimate of 4 5 ma for the lochkovian use of the eccentricity periodicity gives a duration for the barrandian lochkovian of 12 16 ma which agrees with the previous geochronometric estimates of 12 2 and 12 5 ma for the lochkovian in any case the cyclic nature of the msec data established by the msszs can be explained by variations in the rate of supply of weathered terrigenous paramagnetic grains to the marine system these variations in supply occurred due to climate changes resulting from the either the obliquity or eccentricity of the earth s orbit knowledge of the periodicity of lochkovian cycles in the barrandian area allows estimation of the rates of sediment accumulation the duration of fossil ranges and the rates of evolution depending on the choice of obliquity or eccentricity to explain the cyclicity in the barrandian lochkovian the estimated rate of sediment accumulation in the gssp outcrop averaged either 51 or 140 ka m the range of the graptoloid monograptus uniformis angustidens wholly contained within the lochkovian sequence at the gssp is also estimated at either 51 or 140 ka

on the characteristics and origin of closed depressions in loess derived soils in europe a case study from central belgium abstract a closed depression cd is a landform where the hillslopes encircle a common sediment depository and the sediment eroded from the surrounding hillslopes is trapped in the system despite the fact that closed depressions cds have been regularly reported in the literature little research on their origin exists therefore a case study was made of the morphological characteristics and genesis of cds in central belgium that are still visible in the landscape through field surveys 26 cds were found in a 43 km2 study area southwest of leuven most cds were situated on a plateau far from villages but close to important rural roads the morphological features of the cds i e diameter area maximum depth and steepest slope were measured the results show that there were significant differences between the morphology of the cds under forest and under cropland cds under cropland were larger shallower and had gentler slopes compared to those under forest based on these morphological features a hypothetical evolution scheme of cds was formulated through a detailed literature search eight out of 26 cds were identified as having an anthropogenic origin they were former quarries mines for calcareous sandstone or iron sandstone in four other cds augerings were made and detailed studies of their soil profiles within and in the vicinity of cds indicated that they are quarries for calcareous loess in one of the four cds with a catchment area of 0 588 ha the soil erosion rate was calculated using soil sequences phosphate content and charcoal analysis since 1950 ad the mean annual soil loss due to water and tillage erosion within the catchment of the cd ranged between 5 5 and 9 8 ton ha or 0 37 0 65 mm based on 14c dating it was calculated that mean annual soil loss since 430 ad amounted to 2 1 ton ha or 0 14 mm

facies discrimination in a mixed fluvio eolian setting using elemental whole rock geochemistry applications for reservoir characterization abstract fluvio eolian successions are generally characterized by a high degree of complexity and internal heterogeneity quantifying the rapid facies changes in time and space is a major challenge to characterization of hydrocarbon reservoirs we present a method for facies discrimination in fluvio eolian successions the method presented here is developed on the modern fluvio eolian sediments from the skeleton coast dune field namibia the examined sediments comprise eight different facies types eolian dune sands interdune fluvial channel sands intraerg mass flow deposits intraerg hyperconcentrated flow deposits fluvial channel sands fluvial mud lacustrine heterolithic sand and lacustrine heterolithic mud the contrasting provenance of the fluvial and eolian sediments results in a distinct source fingerprint which can be discriminated using elemental whole rock geochemistry a multivariate statistical technique performed on the geochemical data has enabled discrimination of seven of the eight facies types furthermore the facies discrimination method allowed a quantitative estimate of the degree of fluvial reworking of eolian sand the skeleton coast dune field was chosen as a test area for geochemical facies discrimination because of its remarkable difference between the immature fluvial source and the mature quartz rich eolian source we hope that the method presented here can be applied to subsurface data from geological settings with the same difference in fluvial and eolian sources it is furthermore hoped that the method can be used in more complex sedimentological settings

gis based simulation of erosion and deposition patterns in an agricultural landscape a comparison of model results with soil map information abstract this paper presents a relatively simple two dimensional hillslope erosion deposition model the model differs from most geomorphological models in that it does not assume that erosion by surface wash is always transport limited as a first test the model is applied to an agricultural catchment in central belgium here patterns of past erosion and deposition can be deduced from information contained in the belgian soil map so that a qualitative validation of the model results is possible the results indicate that a simple model formulation allows to reproduce the basic pattern of erosion and deposition as it is observed in the landscape this confirms the major influence of topography on erosion and deposition patterns in such landscapes and indicates that in some cases a simple model formulation may well be sufficient to allow adequate modelling of landscape evolution

evaluating choices in multi process landscape evolution models the interest in landscape evolution models lems that simulate multiple landscape processes is growing however modelling multiple processes constitutes a new starting point for which some aspects of the set up of lems must be re evaluated the objective of this paper is to demonstrate the practical significance of and possibilities for such re evaluation we first discuss which simplifications must be made to set up lems then simplifications of particular interest to the modelling of multiple processes are identified finally case studies from new zealand belgium and croatia explore the performance of different model versions under several common choices for model and data simplifications in these case studies we illustrate methods to make the choices typically by i comparing the results of different model versions ii assessing model validity or iii indicating the sensitivity of models for different simplifications the results indicate that lem performance is strongly dependent on multi process related choices and that performance indicators can be used for ex post testing of the influence of these choices in particular we demonstrate the significance of simplifications regarding the number of processes presence of sinks and temporal resolution

magnetosusceptibility event and cyclostratigraphy method applied to marine rocks detrital input versus carbonate productivity magnetic susceptibility data from marine rocks can be used for global correlation due to synchronous variations in global erosion we show here that the magnetic susceptibility signature found in two forms resides mainly in paramagnetic and other detrital constituents in most marine rocks the first form is a short term low magnitude high frequency cyclic climate signature that is often useful for regional correlation the second form is a longer term higher magnitude low frequency signature resulting from transgressive and regressive events that can be used for global correlation fluctuations in detrital input due to eustatic based erosion are the primary cause of events these fluctuations are driven by large scale processes such as global orogenic cycles however variations in carbonate productivity cannot be ruled out when explaining the low magnitude climate driven cyclicity also observed in magnetic susceptibility data sets

a temporarily changing holocene sediment budget for a loess covered catchment central belgium abstract this study presents a holocene sediment budget for the nethen catchment a typical river catchment 55 km 2 in the belgian loess belt soil erosion and hillslope sediment storage are quantified by extrapolating detailed data obtained from soil profile truncation studies in three representative zero order sub catchments floodplain sediment storage is estimated by augerings along several transects across the main river and some of its tributaries the sediment budget shows that ca 38 of the soil eroded during the holocene is redeposited as colluvium on hillslopes and in dry valley bottoms another 23 of the eroded sediment is now stored as alluvium in the floodplain the remaining 39 or 21 10 6 mg is exported from the catchment dating of both colluvial and alluvial sediment deposits reveals that sediment dynamics between the hillslopes the dry valley bottoms and the floodplain behave highly non linearly before 500 bc sediment delivery from the hillslopes to the river channels was near maximum however since the onset of significant agriculture in the late bronze age early iron age increased rates of soil erosion are only reflected in the colluvium but not in the floodplain resulting in very low hillslope sediment delivery ratios from the medieval period onwards soil erosion increased even further mainly as a result of a further increase in agricultural land use but now also accelerated floodplain sedimentation took place due to an improved slope channel coupling and the management of floodplains

removing infragravity wave induced noise from ocean bottom seismographs obs data deployed offshore of taiwan abstract vertical ocean bottom seismograph obs data at frequencies below 0 05 hz are contaminated by noise induced by infragravity waves we constructed the transfer function between pressure and velocity data from obss deployed in taiwan waters to remove the wave pressure induced noise from seismic recordings data were analyzed from five portable broadband obss deployed each for 10 months at water depths from 1740 to 4600 m and from a cabled shallow buried seismograph eos1 installed on the seafloor at 300 m depth removing long period noise from these obs data improves the identification of teleseismic phases such as p s ss p diff and pkikp that are otherwise ambiguous or unidentifiable for eos1 infragravity wave signals completely mask the p and s waveforms in the 10 50 s period band suitable for centroid moment tensor cmt solutions for most of the local events application of the transfer functions to predict and remove wave deformation yielded clean prominent p and s waveforms at these periods and aided in the cmt determination for small events jointly with land stations the relative amplitudes of the wavenumber normalized transfer function for some of the obss are mostly determined by the thickness of the sediment at the obs site

the effect of spatial heterogeneities on geomorphic expression in a model of basin evolution spatial variability is a basic component of all natural systems the system being studied here is the topography of an evolving drainage basin spatially heterogeneous erosivity within the drainage basin influences the structure of the drainage network the roughness of small scale features and the overall appearance of the simulated topography the presence of heterogeneities does not simply blur and smear analytical relationships the heterogeneities themselves introduce new structure to the organization of the drainage basin three measures the slope area relationship the cumulative area relationship and the hypsometric distribution are all systematically affected by spatial heterogeneity we will demonstrate how and why these relationships are affected and also how different structures in the heterogeneities themselves are manifested in the resulting simulated topography

cenomanian turonian and δ13c and δ18o sea level and salinity variations at pueblo colorado stable isotopes of the surface dwelling planktic foraminifera hedbergella planispira its abundance variations and mineralogical analysis of the cenomanian turonian at pueblo co reveal cyclic variations in surface salinity due to changes in precipitation freshwater influx marine incursions and long term sea level fluctuations hedbergella planispira is a proxy for salinity variations as indicated by 2 4 more negative 18o values in intervals of peak abundances as compared to intervals with reduced populations negative 18o values reflect periods of brackish surface waters caused by freshwater influx during wet humid periods accompanied by increased clastic transport more positive 18o values reflect more normal marine salinities as a result of arid periods and or marine incursions and correlate with intervals of increased biogenic carbonate deposition the magnitude of salinity variations during the low sea level of the hartland shale is twice that during the sea level transgression of the bridge creek limestone the rapid positive 13c shift that marks the onset of oceanic anoxic event 2 oae 2 at pueblo occurred over a period of about 100 ky 93 90 94 00 ma and coincided with the major sea level transgression that culminated in the deposition of the basal bridge creek limestone a positive 13c shift also occurred in the rotalipora cushmani zone prior to oae 2 and coincided with a sea level rise and enhanced preservation of terrestrial organic matter the likely cause for oae 2 is depletion of 12c in the water column as a result of high primary productivity whereas an earlier r cushmani zone event was primarily caused by increased input of terrigenous organic matter both 13c events are associated with enhanced organic matter preservation and anoxic or dysoxic bottom waters

geochemical and sedimentological control of the magnetic properties of hemipelagic sediments owing to their high sedimentation rates and wide areal extent hemipelagic sediments along continental borderlands are potentially important high resolution recorders of geomagnetic secular variation to assess this possibility we studied suboxic hemipelagic muds from the oregon continental slope and anoxic laminated diatomaceous oozes from the gulf of california these sediments were rapidly deposited with average sedimentation rates of 121 and 135 cm kyr respectively bulk sediment sedimentological and geochemical analyses indicate that the two areas represent contrasting depositional regimes the remanence in both environments resides in fine grained magnetite particles although minor amounts of hematite were observed in the topmost gulf of california sediments despite first order differences the sediments from both areas show similar downcore patterns of systematic increases in solid sulfur mainly as pyrite dramatic decreases in natural nrm anhysteretic and isothermal remanent magnetization intensities and accompanying shifts in the magnetic stabilities these changes are consistent with reduction and dissolution of the ferrimagnetic iron oxides with depth due to early diagenesis of organic matter the magnetic grain size distribution first appears to rapidly coarsen downcore as the smallest and most abundant grains are removed then slowly grows finer as the remaining particles dissolve no evidence was observed for authigenic formation of magnetite provided sufficient concentration and stability of the detrital magnetic particles paleomagnetic directions can survive this dissolution diagenesis however relative paleointensity determinations based on normalization of nrm by concentration in related parameters will give erroneous estimates of paleofield behavior in such diagenetically altered sediments

two dimensional modelling of the within field variation in rill and gully geometry and location related to topography abstract the topography rill pattern and geometry were surveyed within a small agricultural field the rill network and dimensions were converted to a grid based system and used to calculate the slope gradient and contributing area for each grid cell a strong correlation was found between the rill cross sections and a power function of slope gradient and contributing area the slope and area exponents were 1 28 and 0 89 respectively for all rill points and 1 02 and 0 87 respectively for the rill points not lying in the depositional area these exponents are within the range reported for field studies in a one dimensional context our data confirmed the potential of an inverse slope area relationship with an area exponent of 0 5 to predict areas prone to rilling and the location of ephemeral gullies however the prediction of individual rill starting points was not possible because of the major influence of small local variations in topography on overland flow discharge both the prediction of the rill cross sections and the prediction of the location of the two ephemeral gullies in the field were significantly improved when the tillage direction was taken into account in calculating the contributing area therefore tillage patterns should be given more attention when developing routing procedures for hydrological and erosion models

from water to tillage erosion dominated landform evolution while water and wind erosion are still considered to be the dominant soil erosion processes on agricultural land there is growing recognition that tillage erosion plays an important role in the redistribution of soil on agricultural land in this study we examined soil redistribution rates and patterns for an agricultural field in the belgian loess belt 137cs derived soil erosion rates have been confronted with historical patterns of soil erosion based on soil profile truncation this allowed an assessment of historical and contemporary landform evolution on agricultural land and its interpretation in relation to the dominant geomorphic process the results clearly show that an important shift in the relative contribution of tillage and water erosion to total soil redistribution on agricultural land has occurred during recent decades historical soil redistribution is dominated by high losses on steep midslope positions and concavities as a result of water erosion leading to landscape incision and steepening of the topography in contrast contemporary soil redistribution is dominated by high losses on convex upperslopes and infilling of slope and valley concavities as a result of tillage resulting in topographic flattening this shift must be attributed to the increased mechanization of agriculture during recent decades this study shows that the typical topographical dependency of soil redistribution processes and their spatial interactions must be accounted for when assessing landform and soil profile evolution

stepwise extinction of larger foraminifers at the cenomanian turonian boundary a shallow water perspective on nutrient fluctuations during oceanic anoxic event 2 bonarelli event a two step pattern in the extinction of larger foraminifers is recorded in the upper cenomanian shallow water carbonates of the southern apennines italy the first step eliminated the alveolinids the most extreme oligotrophs and reduced dramatically the diversity of larger foraminifers the second step wiped out the few survivors seemingly able to tolerate mesotrophic conditions leaving a disaster fauna dominated by small heterotrophs this pattern of extinction parallels the ecological succession of shallow water benthic foraminiferal assemblages along a gradient of increasing nutrient availability high resolution carbon isotope stratigraphy shows that the extinction of alveolinids was contemporaneous with the extinction of rotaliporid planktic foraminifers the drowning of certain tethyan carbonate platforms and an episode of thermal instability recorded in sea surface temperature in the open ocean ocean stratification during the first phase of oceanic anoxic event 2 would have promoted oligotrophic conditions in surface tropical waters and maximum diversity of larger foraminifers following this ocean overturning caused by surface water cooling is credited with delivering to shallow water environments the excess nutrient loads previously stored at depth triggering the environmental changes leading to stepwise extinction of larger foraminifers

shear wave splitting at the edge of the ryukyu subduction zone abstract intraslab events recorded by ocean bottom seismometers in the okinawa trough provide an extended depiction of shear wave splitting in the southwest section of the ryukyu subduction zone at 100 200 km from the western edge of the subduction system we observed trench normal fast polarization direction in the back arc compatible with 2d slab or rifting driven corner flow towards the edge the fast directions are sub parallel to the trench in the arc back arc region and rotate to trench normal within 50 km of the edge splitting constrained by land stations with paths mostly in the mantle wedge exhibits similar trench normal fast directions in the subduction edge zone further inland the dominant component of fast directions becomes roughly parallel to the taiwan orogenic fabric splitting of p to s phases converted at the moho of the okinawa trough and of s phases from shallow events suggest that crustal anisotropy may affect the measured splitting but the observed pattern reflects predominantly mantle anisotropy the variation in splitting along the okinawa trough cannot be explained by a b type a type olivine fabric transition in the mantle wedge it may indicate the presence of an along arc flow in the mantle wedge towards the edge where it is blocked and deflected by the eurasian lithosphere this scenario bolsters previous studies suggesting a significant impact of eurasian lithosphere on the dynamics of the ryukyu subduction system

the compatibility of erosion data at different temporal scales abstract soil erosion processes have been studied intensively throughout the last decades and rates have been measured at the plot scale as well as at larger scales however the relevance of this knowledge for the modelling of long term landscape evolution remains a topic of considerable debate some authors state that measurements of current rates are irrelevant to landscape evolution over a longer time span as they are inconsistent with some fundamental characteristics of landscapes such as the fact that the long term sediment delivery ratio needs to be equal to 1 and that extrapolation of current rates would imply that all soils in europe should have disappeared by now e g parsons a j wainwright j brazier r e powell d m 2006 is sediment delivery a fallacy earth surface processes and landforms 31 1325 1328 in this study we investigate if and to what extent estimates of long term erosion rates are consistent with information obtained over much shorter time spans for the loam belt of belgium in a first step observed short term and long term patterns in the belgian loess area are compared statistically by classifying the study area into landscape element classes and comparing average erosion values per class this analysis shows that the erosion intensities on the two temporal scales are of the same order of magnitude for each landscape element class next the spatially distributed model watem lt water and tillage erosion model long term is calibrated based on the available short term data by optimising average erosion values for the same landscape element classes finally the calibrated model is used to simulate long term landform evolution and is validated using long term data based on soil profile truncation we found that the model allows simulating landscape evolution on a millennial time scale using information derived from short term erosion and deposition data however it is important that land use is taken into account for the calibration in order to obtain realistic patterns on a longer time scale our analysis shows that at least for the study area considered data obtained on erosion and deposition rates over various temporal scales have the same orders of magnitude thereby demonstrating that measurements of current rates of processes can be highly relevant for interpreting long term landscape evolution

cretaceous oceanic anoxic event 2 triggered by a massive magmatic episode oceanic anoxic events oaes were episodes of widespread marine anoxia during which large amounts of organic carbon were buried on the ocean floor under oxygen deficient bottom waters oae2 occurring at the cenomanian turonian boundary about 93 5 myr ago is the most widespread and best defined oae of the mid cretaceous although the enhanced burial of organic matter can be explained either through increased primary productivity or enhanced preservation scenarios the actual trigger mechanism corresponding closely to the onset of these episodes of increased carbon sequestration has not been clearly identified it has been postulated that large scale magmatic activity initially triggered oae2 refs 4 5 but a direct proxy of magmatism preserved in the sedimentary record coinciding closely with the onset of oae2 has not yet been found here we report seawater osmium isotope ratios in organic rich sediments from two distant sites we find that at both study sites the marine osmium isotope record changes abruptly just at or before the onset of oae2 using a simple two component mixing equation we calculate that over 97 per cent of the total osmium content in contemporaneous seawater at both sites is magmatic in origin a approximately 30 50 fold increase relative to pre oae conditions furthermore the magmatic osmium isotope signal appears slightly before the oae2 as indicated by carbon isotope ratios suggesting a time lag of up to approximately 23 kyr between magmatism and the onset of significant organic carbon burial which may reflect the reaction time of the global ocean system our marine osmium isotope data are indicative of a widespread magmatic pulse at the onset of oae2 which may have triggered the subsequent deposition of large amounts of organic matter

faulting and hydration of the upper crust of the sw okinawa trough during continental rifting evidence from seafloor compliance inversion the elastic response of seafloor to ocean gravity wave loading or seafloor compliance provides a constraint on the elastic properties of the crust we measured seafloor compliance at three ocean bottom seismometer obs sites around taiwan two in the southwestern sw okinawa trough and one on the ryukyu arc and performed inversion for crustal structures beneath them models best fitting the data demonstrate a decrease in upper crustal shear velocity and an increase in the compressional shear velocity ratio from the arc site to the trough sites with increasing amount of back arc extension this variation suggests that the upper continental crust is highly faulted and hydrated during rifting of the eurasian lithosphere

characteristics and controlling factors of old gullies under forest in a temperate humid climate a case study from the meerdaal forest central belgium abstract in many forests of northwestern europe old gullies can be found but few studies have reported their genesis and characteristics this study investigates these old gullies under forest in the large case study area of meerdaal forest in the central belgian loess belt the objectives are 1 to determine the spatial distribution of these gullies 2 to measure their morphological and topographical characteristics and 3 to reconstruct the factors that led to their development in the 1329 ha study area 252 channel like incisions were mapped different types of incisions could be distinguished besides small and large gullies many incisions were sunken lanes or road gullies these road gullies are aligned along north south oriented lines whereas the concentration of old gullies is strongly related to the distribution of archaeological sites out of the 252 mapped incisions 43 large gullies and 21 representative road gullies were selected for detailed morphological and topographical measurements the characteristics of these two types of incisions were compared with ephemeral gullies formed under nearby cropland significant differences in morphology between the three types could be demonstrated ephemeral gullies under cropland and large gullies under forest differ significantly in all measured parameters except bottom width both the old gullies and road gullies under forest have a significantly larger cross section and total eroded volume compared with the ephemeral gullies observed under cropland this indicates that once formed the old gullies were not ploughed in nor were they filled by sediment originating in their drainage areas because of limited sediment production comparing topographical characteristics i e slope at the gully head and runoff contributing area of forest gullies and ephemeral gullies that formed under cropland yields important indications about their formation the larger sedimentation slope of forest gullies compared with ephemeral gullies and road gullies suggests that the forest gullies incised on vegetated slopes as a consequence of runoff from the adjacent plateau where the forest cover was disturbed for the old gullies under forest no relation between slope at the gully head and runoff contributing area is observed probably because most gullies occur on very steep slopes when simulating arable land use in the study area zones where ephemeral gullies are expected to develop can be predicted using published topographical threshold relationships comparing the zones where ephemeral gullies are predicted with the position of old gullies under forest leads to the conclusion that gully incision was most probably not triggered by extreme rainfall events and that they are not of periglacial origin the observed gully pattern can best be explained by local anthropogenically determined land use changes

reconstructing ancient topography through erosion modelling one of the main aims of geomorphology is to understand how geomorphic processes change topography over long time scales over the last decades several landscape evolution models have been developed in order to study this question however evaluation of such models has often been very limited due to the lack of necessary field data in this study we present a topography based hillslope erosion and deposition model that is based on the watem sedem model structure and works on a millennial time scale soil erosion transport and deposition are calculated using slope and unit contributing area the topography is iteratively rejuvenated by taking into account modelled erosion and deposition rates thereby simulating topographic development backwards in time a first attempt has been made to spatially evaluate the model using detailed estimates for historical soil erosion and sediment deposition volumes obtained from an augering campaign in a small catchment in the belgian loess belt the results show that the model can simulate realistic soil redistribution patterns however further research is necessary in order to deal with artificial flaws that cause routing problems and significantly influence results common problems and issues related to this type of backward modelling are also discussed

multi process late quaternary landscape evolution modelling reveals lags in climate response over small spatial scales landscapes evolve in complex non linear ways over quaternary timespans integrated geomorphological field studies usually yield plausible hypotheses about timing and impact of process activity landscape evolution models lems have the potential to test and falsify these landscape evolution hypotheses despite this potential lems have mainly been used with hypothetical data and rarely to simulate the evolution of an actual landscape in this paper we use a lem lapsus landscape process modelling at multi dimensions and scales to explore if it is possible to test and falsify conclusions of an earlier field study on 50 ka landscape evolution in okhombe valley kwazulu natal south africa in this lem five landscape processes interact without supervision water driven erosion and deposition creep solifluction biological weathering and frost weathering calibration matched model results to three types of qualitative fieldwork observations individual process activity over time relative process activity over time and net landscape changes over time results demonstrate that landscape evolution of the okhombe valley can be plausibly simulated a particularly interesting and persistent feature of model results are erosional and depositional phases that lag climatic drivers both by decades and by several ka within a few hundred meters the longer lag has not been reported for this spatial scale before and may be an effect of slow landscape soil vegetation feedbacks the combined modelling and fieldwork results allow a more complete understanding of these responses to climate change and can fill in hiatuses in the stratigraphical record suggestions are made for methodological adaptations for future lem studies

geophysical and geological signatures of relative sea level change in the upper wheeler formation drum mountains west central utah a perspective into exceptional preservation of fossils abstract the middle cambrian wheeler formation in utah is renowned for its exceptionally preserved fossils herein geophysical techniques gamma ray spectrometry and magnetic susceptibility carbonate analyses lithofacies and fossils are used to characterize limestones and calcareous mudrocks of the upper portion of the middle wheeler formation and the upper wheeler formation in the drum mountains west central utah this succession was deposited on a mixed carbonate siliciclastic ramp within the house range embayment an eastward incursion of deeper water created and bounded on the southeast by a normal fault geophysical data clearly reveal variations in carbonate versus clay content observed patterns among outcrop geophysical data lithofacies and fossils are interpreted within the contexts of relative sea level changes and a sequence stratigraphic model above a basal interval of rhythmically bedded limestones interpreted to have been deposited on the middle part of the ramp during a period of relatively low sea level lithofacies rising gamma ray and rising magnetic susceptibility track a transgression which culminates in a maximum flooding surface mfs this mfs is near the base of a hot zone an 6 m thick interval of exceptional preservation konservat lagerstatte highest magnetic susceptibility highest gamma ray values highest clay content and with a bulk carbonate content of 4 20 the basal layer of this zone contains abundant fully articulated specimens of agnostids and tiny polymerid trilobites exceptionally preserved fossils such as non trilobite arthropods priapulid and annelid worms hyolithids phyllocarid arthropods with soft parts algae and fragile sponges are much more abundant within this hot zone than in other strata of the succession these specimens are preserved in very thin bedded to laminated mudrock only rarely interrupted by macroscopic signs of bioturbation stratigraphically above the hot zone is a thick unit of mudrock in which both gamma ray and magnetic susceptibility decrease gradually at first and then precipitously to very low levels in concert few soft bodied specimens have been recovered from this upper interval the gradual decrease in geophysical responses is interpreted to be the result of gradual shallowing during highstand caused mainly by progradation of the carbonate factory it was followed by an abrupt regression mudrocks are capped by burrow mottled grainstone and stromatolitic boundstone representing a lowstand or the earliest transgressive phase of the next cycle these observations lead to the following conclusions 1 the upper wheeler formation represents most of a third or fourth order cycle of relative sea level change on a mixed carbonate siliciclastic ramp rather than a period of shallow water lagoonal sedimentation as previously proposed 2 superimposed on this overall cycle are several perhaps many higher order fluctuations in relative sea level 3 when the present results are coupled with results of earlier workers who interpreted the lower and middle wheeler formation as a major transgression and regression the wheeler formation of the drum mountains involves two major sea level cycles rather than one 4 the konservat lagerstatte was preserved in the deepest water early highstand portion of the upper wheeler sequence and 5 these results support earlier hypotheses that konservat lagerstatten in mixed carbonate siliciclastic successions are most likely to occur during late transgression to early highstand given that low energy anoxic conditions prevailed

importance of slope gradient and contributing area for optimal prediction of the initiation and trajectory of ephemeral gullies abstract ephemeral gully erosion rates are controlled by various factors out of which topography plays an important role this study investigates the possibility to predict the location of ephemeral gullies using two topographic attributes only i e local slope gradient s and upslope contributing area per unit length of contour a s an inverse relationship between s and a s in which the relative importance of the area exponent was varied was evaluated as to its performance in predicting the location of ephemeral gullies for three intensively cultivated catchments in the belgian loess belt this model is easily applicable as it only uses information on topography which can be derived from a digital elevation model and land use predicted locations of ephemeral gullies were confronted with the locations recorded over 5 years of field observations for all catchments a high relative area exponent relative to the slope exponent was required to yield good results the optimal relative area exponent ranged from 0 7 to 1 5 however the quality of the prediction did not vary significantly when changing the exponent within this range an average relative area exponent of ca 1 is appropriate for all three study areas and may therefore be proposed for similar areas under similar conditions a striking discrepancy was found between the high relative area exponent required to predict optimally the trajectory of the gullies and the low relative area exponent 0 2 required to identify the spots in the landscape where ephemeral gullies begin this indicates that spots in the landscape where gullies start are more controlled by slope gradient while the presence of concavities control the trajectory of the gullies until the slope gradient is too low and sediment deposition starts no relationship was found between the frequency of the occurrence of ephemeral gullies and the percentage of predicted gully pixels for each frequency class this indicates that frequently occurring gullies at the same location are not easier to predict than accidental gullies

geochemistry of pelagic and hemipelagic carbonates criteria for identifying systems tracts and sea level change the elemental si ti al mn ca zr and carbon stable isotope 13 c geochemistry of a biostratigraphically well constrained cenomanian turonian upper cretaceous chalk succession on the isle of wight southern england shows systematic variation that corresponds closely to a published sequence stratigraphic model for the cenomanian six sequences and their constituent systems tracts defined elsewhere using sedimentological criteria are clearly distinguishable from bulk sediment elemental profiles and an additional upper cenomanian sequence previously identified in spain is recognized in england from these geochemical data the manganese curve is particularly instructive exhibiting minima around sequence boundaries and through lowstands rising values from the transgressive surfaces through transgressive systems tracts maxima around maximum flooding surfaces and declining values through highstands silica and trace element ti zr aluminium ratios peak around transgressive surfaces and maximum flooding surfaces indicating pulses of increased siliciclastic input positive 13 c excursions are confirmed at the base of the middle cenomanian and spanning the cenomanian turonian boundary but are not evident in other sequences variation in mn is related to bulk sedimentation rate and detrital versus biogenic supply which control the mn flux and the efficiency of the diagenetic mn pump that leads to elevated mn contents in sediments manganese peaks do not generally correlate with positive 13 c excursions and although near coincident mn and 13 c peaks occur around the cenomanian turonian boundary the former is not necessarily linked to the oceanic anoxic event occurring at that time the global oceanic mn flux may have been enhanced during the cenomanian as a result of hydrothermal activity during rapid sea floor spreading and oceanic plateau formation elemental chemostratigraphy provides a new tool for developing sequence stratigraphic models in pelagic and hemipelagic carbonate successions

soil erosion and sediment deposition in the belgian oess belt during the holocene establishing a sediment budget for a small agricultural catchment a method to establish a holocene sediment budget for a 103 ha agricultural catchment representative for the belgian loess belt is presented soil erosion and sediment deposition were determined based on 185 coring locations and a large excavation in the valley bottom results were integrated in a gis and interpolation techniques applied to derive spatial patterns of erosion and sedimentation total soil erosion sediment deposition and sediment export were calculated and the results show that volumes are highly dependent on the interpolation technique used sediment delivery ratios between 20 and 42 are derived and are consistent with data reported in previous studies this clearly shows that the majority of the sediments produced during the holocene have been stored near their source area and have not been delivered to the downstream rivers the spatial distribution of soil erosion and sediment deposition within the catchment is strongly dependent on slope gradient and position within the catchment which suggests that since human impact began topography has been the main factor determining long term soil erosion and sedimentation

pattern and rate of erosion inferred from inca agricultural terraces in arid southern peru abstract earthworks of assumed age and their initial and current morphologies provide an ideal basis for developing and testing models for long term landform erosion inca agricultural terraces abandoned at 1532 a d in the drylands of southern peru may be used to document morphological changes since the abandonment the objective of this research is to determine the erosion pattern and process to estimate the erosion rate the development of rills and channels on the inca agricultural terraces is evidence for erosion by wash processes on slopes where the anchoring effect of vegetation is absent and loose material is available for removal the pattern and amount of erosion from 1532 2005 a d is estimated by comparing elevation models of the observed morphology and reconstructed models of the original morphology of the inca terraces the results show that in areas of sediment accumulation surface elevation increased up to 0 5 m elevation lowering on the terrace treads was 0 7 m at maximum and a temporally and spatially averaged lowering rate was 0 094 mm yr 1 this gives insights about how the rate of erosion occurs on currently disturbed lands in arid environments where soil resources are scarce and lands are prone to desertification

evidence for a change in the periodicity of tropical climate cycles at 2 4 myr from whole core magnetic susceptibility measurements the earth s orbit about the sun is influenced by gravitational interactions with the moon and other planets the resulting orbital perturbations give rise to cyclical variations in orbital eccentricity obliquity and precession with periods of 100 41 19 and 23 kyr respectively1 these variations are climatically important because they affect the seasonal and latitudinal distribution of solar radiation magnetic susceptibility measurements in deep sea sediment cores can be used as a sensitive indicator of temporal variations in the concentration of terrigenous material supplied to the sea bed here we use this approach to study the evolution of cycles of terrigenous sedimentation at ocean drilling program sites in the arabian sea and the eastern tropical atlantic we show from spectral analyses of the two susceptibility time series spanning the past 3 2 3 5 myr that the records are driven strongly by orbital forcing before 2 4 myr before present bp both records are strongly influenced by the 23 and 19 kyr periodicities but after 2 4 myr they are both significantly influenced by the 41 kyr periodicity this shift coincides with the beginning of major northern hemisphere glaciation which indicates for the indian ocean site that the supply of terrigenous sediment carried by monsoonal winds has responded to the rapid increase in ice cover at this time we cannot however exclude possible effects of changes in bottom water circulation on the susceptibility record of the atlantic site

the cenomanian turonian boundary event oae2 and palaeoenvironmental change in epicontinental seas new insights from the dinocyst and geochemical records abstract organic walled dinoflagellate cyst dinocyst and geochemical records across the cenomanian turonian boundary ctb are presented for the nw european reference section at eastbourne england dinocyst and nannofossil fertility indexes indicate that an upwelling driven productivity pulse accompanied a eustatic sea level fall that preceded by at least 40 kyr the global rise in 13 c values that marks the onset of oceanic anoxic event 2 oae2 and the deposition of black shales in the deep ocean a marine productivity collapse in the latest cenomanian is evidenced by the falling absolute and relative abundance of peridinioid dinocysts believed to be the product of heterotrophic dinoflagellates this biotic change accompanied transgression and sharply rising sea surface temperatures following an atlantic wide episode of short lived cooling geochemical tracers provide evidence of caribbean colombian plateau volcanism the increase in water depth caused by the latest cenomanian transgression resulted in less eutrophic waters in epicontinental seas where ctb biotic turnover was driven largely by water mass changes rather than oxygen depletion the species richness absolute abundance ratio of dinocysts is proposed as a water mass stability proxy

siderite formation in anoxic deep sea sediments a synergetic bacteria controlled process with improtant implications in paleomagnetism recent work on magnetic properties of limestones has demonstrated that the mineral siderite can be very important in paleomagnetism for two reasons first oxidation of siderite produces secondary daughter magnetic minerals magnetite maghemite and hematite either before during or after sampling these daughter products can completely change the magnetic properties of limestone samples and if unrecognized may be one of the primary reasons why many paleomagnetic studies of limestones especially paleozoic limestones are unsuccessful second siderite in weakly magnetized rocks may indicate the potential for successful paleomagnetic results because the presence of siderite indicates that the primary magnetic carriers are still intact appropriate demagnetization methods should yield successful results we conclude that microenvironmental conditions in anoxic marine sediments may permit the formation of siderite from iron ii produced during bacterial dissimilatory iron reduction

geochemical and climatic effects of increased marine organic carbon burial at the cenomanian turonian boundary perhaps the most significant event in the cretaceous record of the carbon isotope composition of carbonate1 2 other than the 1 2 5 negative shift in the carbon isotope composition of calcareous plankton at the cretaceous tertiary boundary3 is the rapid global positive excursion of 2 13c enrichment which took place between 91 5 myr and 90 3 myr late cenomanian to earliest turonian c t boundary event 1 4 5 this excursion has been attributed to a change in the isotope composition of the marine total dissolved carbon tdc reservoir resulting from an increase in rate of burial of 13c depleted organic carbon which coincided with a major global rise in sea level5 during the so called c t oceanic anoxic event oae 6 here we present new data from nine localities which demonstrate that a positive excursion in the carbon isotope composition of organic carbon at or near the c t boundary7 8 is nearly synchronous with that for carbonate and is widespread throughout the tethys and atlantic basins fig 1 as well as in more high latitude epicontinental seas the postulated increase in the rate of burial of organic carbon may have had a significant effect on co2 and o2 concentrations in the oceans and atmosphere and consequent effects on global climate and sedimentary facies

drainage basin responses to climate change recent investigations have shown that the extent of the channel network in some drainage basins is controlled by a threshold for overland flow erosion the sensitivity of such basins to climate change is analyzed using a physically based model of drainage basin evolution the golem model simulates basin evolution under the action of weathering processes hillslope transport and fluvial bedrock erosion and sediment transport results from perturbation analyses reveal that the nature and timescale of basin response depends on the direction of change an increase in runoff intensity or a decrease in vegetation cover will lead to a rapid expansion of the channel network with the resulting increase in sediment supply initially generating aggradation along the main network followed by downcutting as the sediment supply tapers off by contrast a decrease in runoff intensity or an increase in the erosion threshold will lead to a retraction of the active channel network and a much more gradual geomorphic response cyclic changes in runoff intensity are shown to produce aggradational degradational cycles that resemble those observed in the field cyclic variations in runoff also lead to highly punctuated denudation rates with denudation concentrated during periods of increasing runoff intensity and or decreasing vegetation cover the sediment yield from threshold dominated basins may therefore exhibit significant variability in response to relatively subtle environmental changes a finding which underscores the need for caution in interpreting modern sediment yield data

stability of the astronomical frequencies over the earth s history for paleoclimate studies the expected changes over the past 500 million years in the principal astronomical frequencies influencing the earth s climate may be strong enough to be detectable in the geological records and such effects have been inferred in several cases calculations suggest that the shortening of the earth moon distance and of the length of the day back in time induced a shortening of the fundamental periods for the obliquity and climatic precession from 54 to 35 41 to 29 23 to 19 and 19 to 16 thousand years over the last half billion years at the same time the precessional constant increased from 50 to 61 arc seconds per year the changes in the frequencies of the planetary system due to its chaotic motion are much smaller their influence on the changes of the periods of climatic precession obliquity and eccentricity of the earth s orbit around the sun can be neglected eccentricity periods used for quaternary climate studies may therefore be considered to have been more or less constant for pre quaternary times

bottom water anoxia inoceramid colonization and benthopelagic coupling during black shale deposition on demerara rise late cretaceous western tropical north atlantic 1 the bulk rock geochemistry and inoceramid isotopic composition from cenomanian to santonian finely laminated organic rich black shales recovered during ocean drilling program leg 207 on demerara rise western tropical north atlantic suggest persistent anoxic free h2s conditions within the sediments and short term variations within a narrow range of anoxic to episodically dysoxic bottom waters over a 15 ma time interval in addition to being organic rich the 50 90 m thick sections examined exhibit substantial bulk rock enrichments of si p ba cu mo ni and zn relative to world average shale these observations point to high organic burial fluxes likely driven by high primary production rates which led to the establishment of intensely sulfidic pore waters and possibly bottom waters as well as to the enrichments of cr mo u and v in the sediments at the same time the irregular presence of benthic inoceramids and foraminifera in this facies demonstrates that the benthic environment could not have been continuously anoxic the 13c and 15n values of the inoceramid shell organics provide no evidence of chemosymbiosis and are consistent with pelagic rain as being a significant food source demerara rise inoceramids also exhibit well defined regularly spaced growth lines that are tracked by 13c and 18o variations in shell carbonate that cannot be simply explained by diagenesis instead productivity variations in surface waters may have paced the growth of the shells during brief oxygenation events suitable for benthic inoceramid settlement these inferences imply tight benthopelagic coupling and more dynamic benthic conditions than generally portrayed during black shale deposition by invoking different temporal scales for geochemical and paleontological data this study resolves recent contradictory conclusions e g sulfidic sedimentary conditions versus dysoxic to suboxic benthic waters drawn from studies of either sediment geochemistry or fossil distributions alone on demerara rise this variability may be relevant for discussions of black shales in general

rapid development and infilling of a buried gully under cropland central belgium abstract analysis of contemporary and past gully erosion and infilling processes allowed to reconstruct the long term evolution of a permanent gully system under cropland an active and a buried gully under cropland were investigated the recent sediment deposits within the active gully adjacent to the buried gully showed that the recent gully was filling in at a mean rate of 6 4 cm a 1 in the buried gully several erosion and deposition phases could be identified and the type of deposited sediments revealed a complex infilling history charcoal pottery and brick fragments of different sizes were found at all depths of the gully infilling their age indicates that the first gully incised after the midst of the 17th century most probably in the second half of the 18th century or the early 19th century gully morphology and analogy with the processes in the recent gully indicate that the buried gully filled in rapidly overall five cycles of cut and fill occurred in 350 years or less and four cycles even within little less than a few decades indicating that gully development and infilling under cropland can be very rapid processes

amino acid geochronology of individual foraminifer pulleniatina obliquiloculata tests north queensland margin australia a new approach to correlating and dating quaternary tropical marine sediment cores 1 in this study we demonstrate the utility of amino acid geochronology based on single foraminiferal tests in quaternary sediment cores from the queensland margin australia the large planktonic foraminifer pulleniatina obliquiloculata is ubiquitous in shelf slope and basin sediments of north queensland as well as pantropical oceans fossil tests are resistant to dissolution and retain substantial concentrations of amino acids 2 4 nmol mg 1 of shell over hundreds of thousands of years amino acid d and l isomers of aspartic acid asp and glutamic acid glu were separated using reverse phase chromatography which is sensitive enough to analyze individual foraminifera tests in all 462 pulleniatina tests from 80 horizons in 11 cores exhibit a systematic increase in d l ratios down core d l ratios were determined in 32 samples whose ages are known from ams 14 c analyses in all cases the asp and glu d l ratios are concordant with 14 c age d l ratios of equal age samples are slightly lower for cores taken from deeper water sites reflecting the sensitivity of the rate of racemization to bottom water temperature beyond the range of 14 c dating previously identified marine oxygen isotope stage boundaries provide approximate ages of the sediments up to about 500 000 years for this longer time frame d l ratios also vary systematically with isotope correlated ages the rate of racemization for glu and asp was modeled using power functions these equations can be used to estimate ages of samples from the queensland margin extending back at least 500 000 years this analytical approach provides new opportunities for geochronological control necessary to understand fundamental sedimentary processes affecting a wide range of marine environments index terms 4267 oceanography general paleoceanography 4850 oceanography biological and chemical organic marine chemistry 3022 marine geology and geophysics marine sediments processes and transport keywords queensland margin marine sediment amino acid racemization geochronology foraminifera quaternary stratigraphy citation hearty p j m j o leary d s kaufman m c page and j bright 2004 amino acid geochronology of individual foraminifer pulleniatina obliquiloculata tests north queensland margin australia a new approach to correlating and dating quaternary tropical marine sediment cores paleoceanography 19 pa4022 doi 10 1029 2004pa001059

sediment export by water from an agricultural catchment in the loam belt of central belgium abstract an agricultural drainage basin of 250 ha was selected in the belgian loam belt to evaluate sediment export by water water discharge was continuously measured at the outlet of the catchment and suspended sediment samples were taken proportional with discharge during rainfall events from these samples supended sediment concentration and grain size distribution were determined within the catchment regular surveys were conducted in order to obtain detailed data on vegetation cover soil surface parameters and erosion and sedimentation features important variations in sediment yield were detected at various time scales ranging from a year over a season to one event these variations could be linked with processes occurring within the catchment due to the development of a vegetation cover the suspended sediment concentrations were lower during the summer period than during the winter period for the same discharge the evolution in both suspended sediment concentration and grain size distribution during the winter period is explained by variations in the soil surface state of the fields as well as the development of a rill and gully network the positive hysteresis observed within a single event is explained by taking into account the distance between the sediment source and the catchment outlet and not by sediment flushing our analysis shows that the role of the main factors controlling the geomorphic response of such a catchment can be identified only if measurements at the outlet are complemented by detailed data on the conditions within the catchment catchment model calibration and validation are therefore impossible if this information is lacking

sensitivity of the eastern mediterranean geomorphic system towards environmental change during the late holocene a chronological perspective alluvial and colluvial sediment deposition provide a vital record of environmental change during the holocene firm chronological control on these archives is necessary to enable us to relate sediment dynamics to human activity and climate variability in the eastern mediterranean such relationships are hard to establish due to the lack of spatially well distributed sediment archives with good chronological control this scarcity is problematic with respect to regional scale reconstructions of the temporal variation of sediment dynamics here we present a radiocarbon database n 178 of geomorphological activity collected from multiple distinct sediment archives within the territory of sagalassos in south western turkey the data were grouped according to their sedimentary facies for analysis using cumulative probability distributions cpds and sedimentation rate sr modelling two small scale colluvial valleys where chronological information was abundant were investigated in more detail results show that sedimentation chronology differs between individual nearby cores as it depends strongly on the local geomorphic situation a generalizing approach combining multiple core results yields more widely valid conclusions high sedimentation rates coincided with the initial major anthropogenic disturbance of the landscape and decreased afterwards probably due to hillslope soil depletion cpd and sr analysis indicates that in general colluvial sedimentation rates did not change much from 2000 bc onwards river floodplain sedimentation in contrast increased markedly during the first millennium bc and during recent times and a significant time lag in enhanced sediment deposition between the upper and lower reaches of the river valleys was observed copyright 2012 john wiley sons ltd

colluvial and alluvial response to land use change in midland england an integrated geoarchaeological approach this paper presents geomorphic soils and palaeoecological data from a small sub catchment in the english midlands in an attempt to provide an integrated picture of holocene landscape change the area used has also been the focus of a multi disciplinary and long term archaeological survey raunds area project and so has a wealth of archaeological and historical data which can be related to the environmental record the paper combines these data much of which are only published in the archaeological literature with new interpretations based upon unpublished data and new data particularly from the hillslopes and new radiocarbon dating from the valley floor it is inferred that despite a long history of pastoral and arable agriculture since the neolithic bronze age colluviation on lower slopes significant soil redistribution and overbank alluviation only began to a measurable extent in the late saxon medieval period 9th century ad onwards it is suggested that this is due to a combination of land use factors principally the laying out of an intensive open field system and the establishment of villages combined with a period of extremes in climate well known throughout europe indeed the critical element appears to have been the social changes in this period that created this regionally distinctive landscape which happened to have a high spatial connectivity and facilitated intensive arable production with high tillage rates intense rainfall events during this period could therefore detach and mobilize high volumes of soil and the open field system facilitated transport to slope bases and valley floors the need for detailed and spatially precise land use data in order to interpret accelerated landscape change is stressed

erosional dynamics flexural isostasy and long lived escarpments a numerical modeling study erosional escarpments are common features of high elevation rifted continents fission track data suggest that these escarpments form by base level lowering and or marginal uplift during rifting followed by lateral retreat of an erosion front across tens to hundreds of kilometers previous modeling studies have shown that this characteristic pattern of denudation can have a profound impact upon marginal isostatic uplift and the evolution of offshore sedimentary basins yet at present there is only a rudimentary understanding of the geomorphic mechanisms capable of driving such prolonged escarpment retreat in this study we present a nonlinear two dimensional landscape evolution model that is used to assess the necessary and sufficient conditions for long term retreat of a rift generated escarpment the model represents topography as a grid of cells with drainage networks evolving as water flows across the grid in the direction of steepest descent the model accounts for sediment production by weathering fluvial sediment transport bedrock channel erosion and hillslope sediment transport by diffusive mechanisms and by mass failure numerical experiments presented explore the effects of different combinations of erosion processes and of dynamic coupling between denudation and flexural isostatic uplift model results suggest that the necessary and sufficient conditions for long term escarpment retreat are 1 incising bedrock channels in which the erosion rate increases with increasing drainage area so that the channels steepen and propagate headward 2 a low rate of sediment production relative to sediment transport efficiency which promotes relief generating processes over diffusive ones 3 high continental elevation which allows greater freedom for fluvial dissection and 4 any process including flexural isostatic uplift that helps to maintain a drainage divide near an escarpment crest flexural isostatic uplift also facilitates escarpment retreat by elevating topography in the vicinity of an eroding escarpment thereby increasing channel gradients and accelerating erosion which in turn generates additional isostatic uplift of all the above conditions high continental elevation is common to most rift margin escarpments and may ultimately be the most important factor

cycle calibrated magnetostratigraphy of middle carnian from south china implications for late triassic time scale and termination of the yangtze platform abstract thick successions from the margins of the triassic yangtze platform of the south china block record a transition from carbonate rich facies zhuganpo formation and equivalents to clastic rich facies xiaowa formation and equivalents during the carnian early late triassic that mark the final phase of termination of this long lived platform cyclostratigraphy derived from spectral gamma ray sgr intensity curves was combined with magnetostratigraphy of two sections in guizhou province wayao transect and its upward extension into the geopark wayao in guanling county and the laishike section in zhenfeng county and one location in sichuan province hanwang section the cyclostratigraphy from all the guizhou sections indicates a persistent suite of ca 34 m 9 m and 1 8 m cycles which are consistent with the ratios of orbital climate oscillations caused by long eccentricity 405 kyr short eccentricity 100 kyr and precession 20 kyr the magnetostratigraphy of all sections is consistent with the cyclicity and characteristic sgr features thereby enabling a cycle tuned magnetic polarity scale spanning 2 4 myr the main feature is a 1 3 myr interval of reversed polarity containing brief normal polarity subchrons and this reversed polarity chron appears to correspond to the significant reversed polarity dominated interval spanning the upper half of the trachyceras aonoides through the lower half of the austrotrachyceras austriacum ammonoid zones of the upper julian the lower substage of carnian this magnetostratigraphic correlation implies that the termination of the yangtze platform is coeval with the beginning of the mid carnian episode of climatic disruption in europe which is locally called the carnian pluvial event or wet intermezzo and with the temporary cessation of the platform carbonates in the dolomites the cycle scaled magnetic polarity time scale supports the short tuvalian long norian age model of the late triassic in which the base of the cycle tuned polarity pattern from the newark group of eastern north america is younger than the end of the julian substage

landsoil a model for analysing the impact of erosion on agricultural landscape evolution the purpose of this research was to develop a model for the analysis of agricultural landscape evolution at a fine spatial resolution scale 1 10 m and a medium term temporal scale 10 100 years the model landsoil landscape design for soil conservation under land use and climate change works at a catchment scale and it is based on the stream soil erosion model it is spatially distributed event based and considers interrill rill and tillage erosion as the main processes acting in soil redistribution the specificities of the model include the use of a detailed representation of the agricultural landscape through parameters such as soil surface properties hydrologic pathways and considering a climate component based directly on rainfall events in this paper we present the characteristics of the model and its application to a mediterranean study area the model was subjected to a calibration validation procedure at two different spatial scales field and catchment with a medium term data series of runoff and sediment concentration measurements a number of medium term field and catchment simulations were carried out allowing us to observe landscape evolution under recent and actual agricultural practices and to formulate hypotheses based on changes related to different agricultural patterns and soil uses modelling at a field scale using rill interrill and tillage erosion simulations on reconstructed prior topographic surfaces showed a relationship between observed and simulated topography with a prediction error 15 and a correlation coefficient r of 0 605 a catchment scale analysis of a degraded scenario maximising hillslope runoff with the removal of all the grass strips between fields indicated a global increase of the soil erosion rate 29 with spatial variability depending on the specific soil use type

a climate driven model and development of a floating point time scale for the entire middle devonian givetian stage a test using magnetostratigraphy susceptibility as a climate proxy abstract here we propose an approach to establish a preliminary age chronology for complete stages within the phanerozoic by applying cyclostratigraphic methods that employ high resolution data sets this requires use of geochemical or geophysical data known to serve as a cyclic climate proxy to demonstrate the method we use the magnetostratigraphic susceptibility technique as the basis for fitting a climate model to the givetian stage of the middle devonian system we show a milankovitch eccentricity climate zonation for the givetian that is pinned to time series analyses from outcrop samples from its upper givetian frasnian france and lower eifelian givetian morocco stage boundaries using these data sets we construct a uniform cyclicity model designed to conform to a 405 kyr cyclicity with a duration corresponding to the published duration for the givetian of 4 4 myr kaufmann 2006 to this model we fit two well established conodont zonation schemes thus allowing time estimates for conodont ranges for the givetian indicating a range from 1 8 myr to 100 kyr before extinction of an individual conodont species we then test and adjust the model using independent data sets from the eastern united states adjustments to the initial model yield a duration of 28 climate half cycles zones for the givetian stage and an increased age to 5 6 myr these zones allow high correlation among sections to better resolve timing of major bio events and provide a floating point time scale to which absolute ages can be applied

moment tensor inversion for offshore earthquakes east of taiwan and their implications to regional collision reliable determination of source parameters for offshore earthquakes east of taiwan with mb 5 5 was a difficult task because of the poor azimuthal coverage by local network and the lack of signals at teleseismic distances we take advantage of the recently established broadband array in taiwan for seismology bats to invert seismic moment tensors for 7 such events occurred in 1996 to cope with different patterns of background noise and unknown structural details we utilize variable frequency bands in the inversion and adapt a two step procedure to select best velocity models for individual epicenter station paths our results are consistent with the overall patterns of regional collision and indicate that the resulting compressive stress has caused significant intraplate deformation within the philippine sea plate simulation of the region s geological evolution and orogenic processes should take this factor into account and allow the philippine sea plate to deform internally

reconstructing a prehistoric topography using legacy point data in a depositional environment reconstruction of past topography is an essential step towards the understanding of past landscapes in terms of biophysical patterns and processes and man landscape interactions by archaeologists geomorphologists geologists and soil scientists landscape reconstructions can be based on process knowledge on data or on a combination of both in this case study we focus on a data based approach where knowledge on the geological history is used to interpret and exploit legacy data as part of a landscape reconstruction of a large area of 584 km2 a map of the elevation near 10 000 bc was produced starting from a present day grid digital elevation model gdem that was filtered for human influences we identified the thickness of accumulated sediments over the holocene mapped these and corrected the gdem to map the thickness of holocene sediments we used 72 osl and 14c dated sediment samples 731 recent profile descriptions and 3288 legacy profile descriptions protocols were formulated based on literature and local correlative studies to convert the legacy profile descriptions into estimates of the thickness of holocene sediments with an estimate of the precision the method of kriging with uncertain data was applied to obtain a map validation at 200 independent test locations with certain data showed a mean error of 6 cm and a standard deviation or error of 16 cm which was in accordance with the estimated precision of 16 cm the resulting map indicated zones with marked change that could be studied in more detail future reconstructions could employ both process knowledge and data by combining landscape genesis models with legacy data to map model errors and thus increase the quality of the reconstruction copyright 2013 john wiley sons ltd

topography reconstruction of eroding landscapes a case study from a hummocky ground moraine carbozalf d abstract erosion processes aggravated by human activity have a large impact on the spatial variation of soil and topographic properties knowledge of the topography prior to human induced erosion paleotopography in naturally stable landscapes is valuable for identifying vulnerable landscape positions and is required as starting point for erosion modelling exercises however developing accurate reconstructions of paleotopography provide a major challenge for geomorphologists here we present a set of paleotopographies for a closed kettle hole catchment in north east germany 4 ha obtained through different reconstruction approaches current soil and colluvium thickness estimated from a dataset of 264 soil descriptions using ordinary kriging were used as input for a mass balance or were compared with a set of undisturbed soil thicknesses to estimate the amount of erosion the performance of the different approaches was assessed with cross validation and the count of mispredicted eroded depositional or stable landscape positions the paleotopographic reconstruction approach based on the average thickness of undisturbed soils in the study area showed the best performance this thickness 1 00 m is comparable to the average undisturbed soil thickness in the region and in line with global correlations of soil thickness as a function of rainfall and initial caco3 content the performance of the different approaches depended more on mispredictions of landscape position due to the assumption of a spatially constant initial soil depth than on small variations in this depth to conclude we mention several methodological and practical points of attention for future topography reconstruction studies concerning data quality and availability spatial configuration of data and other processes affecting topography

high resolution magnetic susceptibility and geochemistry for the cenomanian turonian boundary gssp with correlation to time equivalent core abstract the upper cretaceous cenomanian turonian c t boundary represents the most significant thermal climatic event in the mesozoic and it has been well studied here we present a relatively new approach for providing both independent climate based cyclostratigraphic analysis and correlation among c t sections we have collected samples for bulk initial low field magnetic susceptibility ms measurement and high resolution inorganic geochemical analyses from two c t sequences 1 the well defined c t global boundary stratotype section and point gssp located at lake pueblo colorado and deposited in the upper cretaceous western interior seaway of north america and 2 the well studied marlstone and limestone usgs 1 portland core drilled at portland colorado 40 km to the west of the c t gssp comparing the lithostratigraphy chemostratigraphy and magnetostratigraphic susceptibility developed from magnetic susceptibility ms data indicates that the usgs 1 portland core closely compares with the c t gssp sequence using any of the three measures demonstrating that intervals collected and sampled from these two sequences are highly correlated a preliminary magnetostratigraphic susceptibility zonation for the c t boundary is presented to which other ms work can be compared fourier transform ft analysis of the ms data from the gssp when compared with previous ft work using geochemical analysis of portland core samples shows close similarities to the gssp with milankovitch eccentricity obliquity and precession bands well defined in both data sets using this result we assign relative ages to the intervals sampled and evaluate changes in absolute sediment accumulation rates through the c t boundary interval we show that while sediment accumulation rate is relatively high in the upper cenomanian a change toward lower accumulation rates in the gssp section at the c t boundary is due to reduced productivity following the c t extinction events that resulted from global warming associated with oceanic anoxic event 2 oae2 that began in the uppermost cenomanian

gulf of mexico sediment sources and sediment transport trends from magnetic susceptibility measurements of surface samples abstract the magnetic properties from 200 trigger core top and van veen grab sediment samples recovered from throughout the gulf of mexico have been analyzed and used to characterize sediment source and flow pattern distributions magnetic parameters included are anhysteretic remanent magnetism arm and magnetic susceptibility ms measurements results from these measurements are compared to previously determined calcium carbonate percentages and clay and hematite influx trajectories into the gulf of mexico for the same samples reported by balsam and beeson balsam w l and beeson j p 2003 sea floor sediment distribution in the gulf of mexico deep sea res i 50 1421 1444 the arm results give an estimate of magnetic grain size distributions and by analogy grain size distributions in general whereas ms patterns show high detrital sediment accumulation zones within the gulf the dominant influx of modern high susceptibility sediment into the gulf of mexico appears to originate from the red river flow into atchafalaya river basin and out into the gulf from atchafalaya bay with significant additional contributions from the mississippi river through the southwest pass of the mississippi river delta this material then moves across the continental shelf and down through the mississippi canyon into the deep gulf where it is redistributed at depths 3600 m the eastern shelf margins in the gulf offshore from alabama and florida are accumulating calcite or quartz rich medium to fine grained sediment that has a very low or diamagnetic ms signature from the louisiana to texas gulf coast margins ms is moderate to high suggesting a river influx of magnetic constituents from the volcanic fields in new mexico and from igneous and metamorphic sources in the mississippi basin offshore from western mexico the ms is high to moderate but the yucatan shelf margin is characterized by low to diamagnetic ms values due to sediment dominated by calcite sands and oozes a trend that continues to the east onto the west florida shelf additional measurements of samples collected in association with sites characterized by hydrocarbon seepage exhibit anomalously low ms values the samples from the lower shelf and slope areas are typified by iron reduction by bacterial organisms in these samples these results produce anomalous localized lows in the ms trends observed

hydroacoustic ray theory based modeling of t wave propagation in the deep ocean basin offshore eastern taiwan t waves are conventionally defined as seismically generated acoustic energy propagating horizontally over long distances within the minimum sound speed layer in the ocean sofar axis minimum however t waves have also been observed by ocean bottom seismometers in ocean basins at depths greater than the sofar axis minimum previously non geometrical processes such as local scattering at rough seafloor and water sediment interface coupling have been proposed as possible mechanisms for deep seafloor detection of t waves here we employ a new t wave modeling approach based on hydroacoustic ray theory to demonstrate that seismoacoustic energy can propagate to reach deep seafloor previously considered as shadow zone of acoustic propagation our new hydroacoustic simulations explain well the observations of t waves on ocean bottom seismometers at deep ocean basins east of taiwan and shed new light on the mechanism for deep ocean t wave propagation

two station measurement of rayleigh wave phase velocities for the huatung basin the westernmost philippine sea with obs implications for regional tectonics summary a broad band ocean bottom seismometer obs deployed 180 km east of taiwan provides a first glimpse into the upper mantle beneath the westernmost section of the philippine sea or the huatung basin hb we measured interstation phase velocities of rayleigh waves between the obs and stations on the eastern coast of taiwan the phase velocities show smooth variations from 3 8 to 3 9 km s 1 for periods of 25 40 s in this short period range phase velocities are comparable to those characterizing the 15 30 ma parece vela basin of the philippine sea modelling of the finite frequency effect proves the validity of the measurement for the average hb the shear wave velocity models inverted from the 25 to 40 s dispersion show a velocity at lithospheric depths about 0 1 km s 1 lower than that of the west philippine sea which agrees with the age effect derived from the pacific pure path model inversions incorporating the less reliable data above 40 s yield a shear velocity 4 0 km s 1 below 150 km an unrealistic value even for a hotspot plume environment the seismological evidence together with the correlation in seafloor depth suggests that the hb and the parece vela basin may have a similar age this is at odds with the previous geochronological study suggesting an early cretaceous age for the hb thermal rejuvenation of the lithosphere was examined as a potential solution to reconciling the two age models

testing high resolution magnetic susceptibility and gamma radiation methods in the cenomanian turonian upper cretaceous gssp and near by coeval section abstract low field mass specific magnetic susceptibility and gamma radiation spectra grs field and laboratory data sets for two upper cretaceous marine sedimentary sequences representing the cenomanian turonian c t boundary in the western interior seaway in central colorado have been measured sections including the c t global boundary stratotype section and point gssp and a one kilometer distant co eval sequence the s section it has previously been established that both and grs data sets are controlled by detrital eolian fluxes into the marine environment although the effect of weathering if any on these parameters when exposed in outcrop is not well documented in addition these parameters are controlled by differing detrital eolian components that may be derived from different sources or be differentially concentrated within the marine system of great interest is 1 how well these data sets record climate cycles 2 how the and grs data are affected by weathering and 3 how well the two methods support each other reported here are the results of a number of field and laboratory experiments designed to evaluate instruments and how and grs data sets co vary and to test their usefulness as correlation tools in stratigraphy results show that both and 40k data sets from laboratory measurement on samples collected in the field where rocks are relatively fresh are generally well correlated respond closely to climate and the corresponding detrital eolian flux into the marine environment and can be used for a rough proxy for each other however weathering appears to affect the 40k data by removing 40k thus reducing correlation potential although does not appear to suffer as badly in more weathered sections and good correlations between sections remain field grs measurements produce a broadly smoothed data set that regionally can be very useful for correlation although potential global correlations are not tested here using data reported here and comparing these data to a 100 kyr cyclic eccentricity e1 climate model for the upper cretaceous at 93 9 ma shows that and 40k data measured in the laboratory can be used to build floating point time scales that produce essentially equivalent results as do other studies using absolute dates

astronomic calibration of the late eocene early oligocene massignano section central italy we present an astronomically tuned polarity timescale for the late eocene early oligocene based on a cyclic limestone marls sedimentary succession exposed at massignano italy gssp for the eocene oligocene boundary here we applied spectral analysis techniques to the high resolution magnetic susceptibility record the results provide clear evidence of a regular and cyclic signal that allows us to discard a stochastic mechanism as controlling these fluctuations conversely these outcomes reveal the presence of stable and notable periodicities that are in tune with those associated with orbital forcing through a cyclostratigraphic analysis of the rhythmic sedimentary alternations and combination with the results of time series analysis of the proxy record we refine the late eocene portion of the gpts through astronomical tuning of the rhythmic sedimentary alternations to recent astronomically calculated variations of earth s orbit we recalibrated the polarity boundaries ages and the main stratigraphic events recognized throughout the sedimentary record among these an age of 33 714 ma is proposed for the e o boundary

resolving the integral connection between pedogenesis and landscape evolution abstract soil is central in the terrestrial ecosystem linking and providing feedback responses to the other components i e water atmosphere and vegetation however the role of soil in landscape evolution is usually not well acknowledged in modeling landscape evolution soil is only treated as a residue of weathering that is transported and redistributed along the hillslope weathering is considered as a process that produces clays and generates unconsolidated materials available for erosion while pedology has been debating the form of qualitative factorial models for 75 years models for soil water heat solute gas and chemical reactions in a profile have matured as soils are distributed continuously in three dimensions across landscapes the profile models need to consider lateral fluxes this review outlines the role of soil in landscape modeling first we review the role of soil in the current landscape evolution models we then review data and models on soil weathering rates and transport processes we discuss soil profile models that simulate soil formation processes and combined soil landscape evolution models finally we discuss how the models can be tested and validated in the real world and suggest how both soil scientists and landscape modelers can work together to address the grand challenges in modeling earth surface processes

c isotope stratigraphy and paleoenvironmental changes across oae2 mid cretaceous from shallow water platform carbonates of southern mexico the stratigraphic and geochemical record of the mid cretaceous cenomanian turonian oceanic anoxic event 2 oae2 has been studied in numerous tethyan and proto atlantic hemi pelagic pelagic successions but little data comes from nearshore carbonate successions from the proto pacific region here we present the results of a combined stratigraphic and 13c study of c t platform carbonates from southern mexico which were deposited within the proto pacific two scales of sedimentary cyclicity are recognized high frequency peritidal and subtidal cycles 0 4 8 m display little evidence of cycle capping subaerial exposure and are not correlative between sections these relationships suggest that the amplitudes of high frequency sea level changes were minimal during the peak mid cretaceous greenhouse longer term transgressive regressive sequences 18 40 m are correlated between sections and using 13c trends can be correlated with sequences developed in northern europe and india the mexican successions were sampled at a high resolution 10 ky for stable isotopes inorganic organic carbon and oxygen total organic carbon insoluble residues and trace metals the 13ccarb curve matches global trends including 6 distinct isotopic stages permitting identification of oae2 despite the lack of characteristic anoxic facies using the 13ccarb trends we tie the previously identified ammonite planktonic foram and nannofossil biostratigraphy from england and the western interior seaway of colorado into the mexican sections the initiation of oae2 defined by an abrupt positive 3 4 13c shift coincides with a long term sea level rise though the sedimentary expression of the deepening is no greater than that observed for any of the other sea level events across the studied interval oae2 termination transition from gradually decreasing to background 13c values is not associated with a particular sea level trend stratigraphic changes in insoluble residues proxy for continental sediment discharge across oae2 are not correlative between sections and do not show consistent systematic relationships with 13c or sea level variations therefore do not support the hypothesis that oae2 was associated with increased continental derived nutrient influx two peaks in trace metal concentrations coincide with the abrupt increase in 13c ratios onset of oae2 and during the transition from elevated to decreasing 13c values near the c t stage boundary these trends are similar to those recorded in coeval deposits of the western interior seaway and are consistent with the hypothesis that oae2 development was related to the release of reduced metals during the short lived 1 my caribbean oceanic plateau basalt eruption in this scenario oxidation of the metals depleted the existing low dissolved o2 concentrations and thermally buoyant plumes of seawater enriched in biolimiting elements mixed with surface waters stimulated primary productivity and further reduced o2 concentrations leading to widespread anoxia and a large positive 13c shift

paleoclimate proxies for cyclostratigraphy comparative analysis using a lower triassic marine section in south china abstract multiple proxies for paleoclimatic and paleoenvironmental change within sedimentary sequences have been developed but understanding their relationships and their relative strengths or weaknesses are required to access a wealth of untapped paleoclimate information we propose two main criteria for multiple proxy datasets to estimate their individual signal to noise levels and to decipher the relationship between multiple proxies first for proxies affected by similar processes then their time dependent changes should be similar second a paleoclimate proxy that is more sensitive to an external forcing such as astronomical forcing is more useful than those that do not have such a response we introduce two methods to evaluate these criteria 1 hierarchical cluster analysis hca probes the relationships among multiple proxies based on similarities of their oscillation patterns and 2 power decomposition analysis pda tests proxy sensitivity to external climate forcing we evaluate 16 high resolution paleoclimate proxies in detail for their applications in paleoclimatology from the marine lower triassic daye formation at the daxiakou section in the three gorges region of south china which has carbonate claystone cycles deposited on an outer ramp the proxies are spectral gamma ray gamma ray intensity potassium uranium thorium thorium uranium and thorium potassium rock color lightness l redness a and yellowness b magnetic susceptibility measured in both laboratory and outcrop anhysteretic remanent magnetization arm lithologic rank simplified lithologic rank and non carbonate fraction carbonate thickness and couplet thickness hierarchical cluster analysis hca gathers these proxies into groups likely affected by the same process the arm and thorium uranium proxies seem to reflect the hinterland weathering process during the early triassic gamma ray potassium uranium thorium magnetic susceptibility and non carbonate fraction proxies refer to terrestrial input the l a and lithologic rank proxies indicate the productivity the redox state and the relative sea level respectively at this section this case study contributes to the understanding of the sensitivity of these types of proxies within marine strata for deep time paleoclimate and astronomical tuned time scales

upper devonian carbonate platform correlations and sea level variations recorded in magnetic susceptibility abstract this paper concerns the analysis of four outcrops in the frasnian upper devonian of belgium we compare the results of a precise sedimentological analysis with magnetic susceptibility ms data this comparison allows us to improve stratigraphic correlations and to test the relationship between magnetic susceptibility and sea level changes considering the sedimentological study different microfacies have been identified from the external belt dominated by relatively argillaceous open marine facies with crinoids to the biostromal and the lagoonal belt dominated by algae rich muddy facies fourth and third order sequences have also been identified and are probably related to sea level variations magnetic susceptibility data provides us very good fourth order correlations and the link between magnetic susceptibility and different sedimentological parameters is obvious more precisely ms appears to be related to fourth and third order sequences and to microfacies

human induced soil erosion and the implications on crop yield in a small mountainous mediterranean catchment sw turkey abstract many hillslopes in the limestone dominated taurus mountain range sw turkey are characterized by severely depleted soils while a significant amount of sediment is being stored in the valley bottoms the same holds true for the 11 4 km2 endorheic gravgaz basin in the vicinity of the hellenistic roman city of sagalassos in sw turkey previous palaeo environmental research in this basin already yielded both detailed sedimentological and palynological information on sedimentation in the valley bottom and vegetation changes that took place during the last several millennia an adapted watem sedem geomorphic model version was used to simulate the impact of the observed changes in vegetation cover climate and hillslope soil properties on hillslope soil erosion and valley bottom sediment deposition over the last 4000 years the calibrated watem sedem model is able to reconstruct the temporal changes of sedimentation in the valley bottom reasonably well to simulate the impact of historic soil erosion on crop productivity a simple crop yield model was coupled to the reconstructed soil thickness maps the main outcomes are that soil erosion was mainly driven by deforestation and hence anthropogenic activity but the resulting soil erosion did not cause a complete collapse of crop yields on the contrary we were able to quantify that the sediment accumulation in the lower lying valley bottoms compensated at least a part of the loss in crop yield from the hillslopes potential crop yield value changed from 2 80 t ha 1 a 1 before widespread deforestation to 2 58 t ha 1 a 1 during roman imperial times and 2 19 t ha 1 a 1 at present these model approaches are tools that allow us to quantify human impact in the past going beyond traditional qualitative descriptions which will ultimately lead to a better understanding of human environment interactions in the past

the history of soil erosion and fluvial deposits in small catchments of central europe deciphering the long term interaction between humans and the environment a review abstract during the last few decades many case studies focused on the dynamics of fluvial systems in response to hillslope erosion land use impact and climate changes this paper will review the current state of knowledge of the dynamics of past soil erosion and gullying in small catchments

midlatitude shelf seas in the cenomanian turonian greenhouse world temperature evolution and north atlantic circulation 1 an 8 million year record of subtropical and midlatitude shelf sea temperatures derived from oxygen isotopes of well preserved brachiopods from a variety of european sections demonstrates a long term cenomanian temperature rise 16 20 c midlatitudes that reached its maximum early in the late turonian 23 c midlatitudes superimposed on the long term trend shelf sea temperatures vary at shorter timescales in relation to global carbon cycle perturbations in the mid cenomanian and the late turonian two minor shelf sea cooling events 2 3 c coincide with carbon cycle perturbations and times of high amplitude sea level falls although this evidence supports the hypothesis of potential glacioeustatic effects on cretaceous sea level the occurrence of minimum shelf sea temperatures within transgressive beds argues for regional changes in shelf sea circulation as the most plausible mechanism the major carbon cycle event in the latest cenomanian oceanic anoxic event 2 is accompanied by a substantial increase in shelf sea temperatures 4 5 c that occurred 150 kyr after the commencement of the 13c excursion and is related to the spread of oceanic conditions in western european shelf sea basins our oxygen isotope record and published 18o data of pristinely preserved foraminifera allow the consideration of north atlantic surface water properties in the cenomanian along a transect from the tropics to the midlatitudes on the basis of fossil derived 18o estimated w ranges and modeled salinities temperature salinity density ranges were estimated for tropical subtropical and midlatitude surface waters accordingly the cenomanian temperate shelf seas waters have potentially the highest surface water density and could have contributed to north atlantic intermediate to deep waters in the preopening stage of the equatorial atlantic gateway

comparing landscape evolution models with quantitative field data at the millennial time scale in the belgian loess belt this study compares three landscape evolution models and their ability to correctly simulate measured 2500 year landscape evolution in two small catchments in the belgian loess belt watem lt and lapsus both model tillage and water erosion and deposition and have detachment limited descriptions for water erosion and deposition equations in lapsus are more mechanistic than those in watem lt watem ltt resembles watem lt but is a transport limited model all three models are dem based calibration and validation simulations were performed forward in time on 1d transects for four spatial resolutions and backward in time for 2d catchments at 20 m resolution for transects model outputs were compared with discretized observations of transect shape for catchments outputs were compared with point observations of palaeo altitude averaged over landscape element classes for transects the three models performed well resulting in model efficiency factors of 0 92 to 0 99 for calibration and 0 62 to 0 96 for validation however for catchments simulations showed that the transport limited watem ltt model could not realistically simulate long term landscape evolution performance of watem lt and lapsus at catchment scale was similar to that on transects although lapsus has problems with backward calculation tests demonstrate that a transport limited approach cannot be used to model long term landscape evolution in the belgian loess belt which is in agreement with theoretical and empirical understanding of soil erosion processes in this environment the difference in performance between transport limited and detachment limited models is clear only when the models are evaluated in a 2d catchment the lack of such distinction when models were applied in a 1d transect highlights the importance of evaluating landscape evolution models in a 2d setting so that effects of flow convergence divergence can be accounted for copyright 2011 john wiley sons ltd

the southwestern edge of the ryukyu subduction zone a high q mantle wedge abstract the lateral edge of a subduction zone is usually depicted as an opening to the asthenosphere where invigorated dynamics and amplified magmatism take place in this study we present evidence from seismic data suggesting the presence of a cold and dynamically sluggish edge environment at the southwest end of the ryukyu subduction system we measured attenuation or 1 q for p waves from subduction zone events at 100 km depths received by obss in the okinawa trough and land stations in ne taiwan in the okinawa trough 100 200 km from the edge q values are lower than 100 in the vicinity of the edge q values increase from 100 to over 1000 towards taiwan to reconcile arguments from geophysical and geochemical observations we propose that the mantle wedge near the edge has high q values due to low temperatures and probably low water content these may result from coupling of the slab laterally with the thick eurasian lithosphere which inhibits back arc rifting retards subduction and reduces the water supply to the mantle wedge the sw ryukyu subduction system represents a subduction zone edge type distinct from more commonly documented free or warm edges

identifying and removing tilt noise from low frequency 0 1 hz seafloor vertical seismic data low frequency 0 1 hz vertical component seismic noise can be reduced by 25 db or more at seafloor seismic stations by subtracting the coherent signals derived from 1 horizontal seismic observations associated with tilt noise and 2 pressure measurements related to infragravity waves the reduction in effective noise levels is largest for the poorest stations sites with soft sediments high currents shallow water or a poorly leveled seismometer the importance of precise leveling is evident in our measurements low frequency background vertical seismic spectra measured on a seafloor seismometer leveled to within 1 10 4 radians 0 006 degrees are up to 20 db quieter than on a nearby seismometer leveled to within 3 10 3 radians 0 2 degrees the noise on the less precisely leveled sensor increases with decreasing frequency and is correlated with ocean tides indicating that it is caused by tilting due to seafloor currents flowing across the instrument at low frequencies this tilting generates a seismic signal by changing the gravitational attraction on the geophones as they rotate with respect to the earth s gravitational field the effect is much stronger on the horizontal components than on the vertical allowing significant reduction in vertical component noise by subtracting the coherent horizontal component noise this technique reduces the low frequency vertical noise on the less precisely leveled seismometer to below the noise level on the precisely leveled seismometer the same technique can also be used to remove background noise due to the seafloor pressure field up to 25 db noise reduction near 0 02 hz and possibly due to other parameters such as temperature variations

holocene millennial scale productivity variations in the sicily channel mediterranean sea 1 the calcareous nannofossil assemblages of ocean drilling program hole 963d from the central mediterranean sea have been investigated to document oceanographic changes in surface waters the studied site is located in an area sensitive to large scale atmospheric and climatic systems and to high and low latitude climate connection it is characterized by a high sedimentation rate the achieved mean sampling resolution is 70 years that allowed the sicily channel environmental changes to be examined in great detail over the last 12 ka bp we focused on the species florisphaera profunda that lives in the lower photic zone its distribution pattern shows repeated abundance fluctuations of about 10 15 such variations could be related to different primary production levels given that the study of the distribution of this species on the sicily channel seafloor demonstrates the significant correlation to productivity changes as provided by satellite imagery productivity variations were quantitatively estimated and were interpreted on the basis of the relocation of the nutricline within the photic zone led by the dynamics of the summer thermocline productivity changes were compared with oceanographic atmospheric and cosmogenic nuclide proxies the good match with holocene master records as with ice rafted detritus in the subpolar north atlantic and the near 1500 year periodicity suggest that the sicily channel environment responded to worldwide climate anomalies enhanced northern hemisphere atmospheric circulation which has been reported as one of the most important forcing mechanisms for holocene coolings in previous mediterranean studies had a remarkable impact on the water column dynamics of the sicily channel

diagenesis of magnetic minerals in recent haemipelagic sediments rapidly deposited sediments from marine and lake environments are being used increasingly to study decadal to millennial fluctuations in the earth s magnetic field the objectives are to gain more fundamental understanding of the geodynamo and to establish a new dating technique for sediments while lacustrine sections are generally restricted to temperate latitude glacial lakes 20 000 yr old rapidly deposited marine sediments along continental margins potentially offer continuous high resolution yet long term records of geomagnetic secular variation however to interpret the sedimentary magnetic record accurately geochemical processes that affect the reliability of the magnetic signal must be understood we now report downcore magnetic profiles from undisturbed kasten cores taken in rapidly deposited laminated sediments from the gulf of california and in bioturbated haemipelagic muds on the oregon continental slope which give apparently reliable directions but show dramatic decreases in the intensities of natural nrm and artificial arm irm remanences with depth downcore porewater and solid sulphur analyses show concave down decreases in porewater sulphate and systematic increases in pyrite and metastable monosulphides the maximum curvature of the sulphide profile occurs directly below the high magnetization zone combined with other compositional and mineralogical analyses these data suggest that due to oxidative decomposition of organic matter magnetites and other iron oxides become progressively reduced and subsequently sulphidized and pyritized with depth iron reduction seems to occur before sulphide formation changes in magnetic stability parameters are consistent with selective dissolution of the finer sized grains causing downcore coarsening of the magnetic fraction

reconstruction of water column anoxia in the equatorial atlantic during the cenomanian turonian oceanic anoxic event using biomarker and trace metal proxies abstract the occurrence of the biomarker lycopane and the enrichment patterns of redox sensitive trace metals in black shales from demerara rise western tropical atlantic reveal that bottom waters were anoxic during the upper cenomanian and lower turonian at this location bottom waters were clearly oxygen depleted already before oceanic anoxic event 2 oae 2 and continued to be so afterwards furthermore the presence of fossil derivatives of isorenieratene and chlorobactene pigments derived from green sulfur bacteria demonstrates that the waters at the base of the photic zone occasionally contained sulfide i e were euxinic before and after oae 2 low concentrations of derivatives of these pigments are present while much higher concentrations occur within the oae 2 section stratification of the water column must have been strong to sustain euxinic conditions in the photic zone for prolonged periods a substantial drop in the concentrations of isorenieratene and chlorobactene derivatives demonstrates that this stratification temporarily broke down during oae 2 a simultaneous decrease in sea surface temperatures suggests that local ventilation was instrumental in this re oxygenation event a rapid decrease in seawater derived trace metal burial rates at demerara rise occurring in phase with the onset of the anoxia related to oae 2 suggests an approximately synchronous onset of oae 2 in the proto north atlantic

orbital time scale and new c isotope record for cenomanian turonian boundary stratotype previous time scales for the cenomanian turonian boundary ctb interval containing oceanic anoxic event ii oae ii vary by a factor of three in this paper we present a new orbital time scale for the ctb stratotype established independently of radiometric biostratigraphic or geochemical data sets update revisions of ctb biostratigraphic zonation and provide a new detailed carbon isotopic record for the ctb study interval the orbital time scale allows an independent assessment of basal biozone ages relative to the new ctb date of 93 55 ma gts04 the d 13 corg data document the abrupt onset of oae ii significant variability in d 13 corg values and values enriched to almost 222 these new data underscore the difficulty in defining oae ii termination using the new isotope curve and time scale estimates of oae ii duration can be determined and exported to other sites based on integration of well established chemostratigraphic and biostratigraphic datums the new data will allow more accurate calculations of biogeochemical and paleobiologic rates across the ctb

the k t boundary in oman identified using magnetic susceptibility field measurements with geochemical confirmation abstract recognizing distal ejecta marker horizons and correlating these among widely separated sections is typically difficult in the absence of visually distinctive marker beds here we propose a magnetic susceptibility ms field method to locate such horizons and explore the k t boundary interval at abat oman as a test of the method a distinctive pattern of high ms values was used to approximately locate the k t boundary interval in a sequence of platform carbonates which were then sampled in detail whole rock geochemical enrichments in ir v as ni co zn and zr and a large negative carbon isotope anomaly confirmed the inferred boundary location common microspherules whose chemistry reflects the whole rock geochemistry are associated with the boundary interval the association suggests that the microspherules formed during or as a result of the impact the geochemical record at the abat locality shows two levels where ir is high 1 ppb suggesting input from two impacts separated in the section by 1 35 m the upper level is chosen as the boundary interval based on the high ir 1 19 ppb 13c negative excursion 7 and distinctive ms pattern

a 164 ka record of environmental change in the american southwest from a carlsbad cavern speleothem abstract a horizontal core 2 8 m in length drilled from the georgia giant column in carlsbad cavern provides climate information for the last 164 ka forty six alpha spectrometric u series ages determined at intervals of 7 6 cm along the core indicate five periods of deposition and five hiatuses the longest from 136 to 110 ka variations in growth rate 0 to 70 mm ka in the abundance of aragonite chalcedony and fe bearing phases and in 13c indicate that glacial intervals of the last 164 ka ois 6 4 and 2 were much wetter than today as were the colder substages 5d and 5b of ois 5 by contrast during the two warmest periods of the past 164 ka namely ois 5e and 1 there was no deposition on either side of the speleothem suggesting conditions as dry or drier than today the record from carlsbad parallels data from many other sites in the southwestern usa and northern mexico and data from marine sediments and ice cores demonstrating the extent to which ice sheet fluctuations influenced conditions in southern new mexico detailed correlation of 13c values in the georgia giant which range from 6 6 to 0 9 relative to pdb with distant speleothem records and with data from ice cores further documents the linkage of southwestern climate with global scale extent of glaciation values of 18o in the georgia giant core range from 9 7 to 4 7 relative to pdb and average 6 6 18o depleted carbonate in the georgia giant during ois 6 at a time when the world s oceans were enriched in 18o suggests that precipitation during cold intervals was brought largely by pacific air masses in fall winter and spring as a result of the southward displacement of the polar jet stream by the growth of the laurentide ice sheet termination ii marking the end of the penultimate glaciation is well defined in the core s 18o data analytical uncertainties in the radiometric ages do not preclude a start of termination ii as late as 128 ka as suggested by specmap data however data from the georgia giant core are more compatible with an earlier start like that obtained from devils hole and vostok data raising the possibility that early warming was widespread in the u s southwest region by 145 ka

the magneto susceptibility event and cyclostratigraphy msec method used in geological correlation of devonian rocks from anti atlas morocco magneto susceptibility event and cyclostratigraphy msec is used here as a means of establishing sensitive chronostratigraphic markers and chronohorizons useful for high resolution correlation msec is a composite of the magnetic susceptibility ms record of marine strata and the coeval biostratigraphic record and similar to chronozones zones based on msec data have boundaries that are isochronous ms a measure of the concentration of magnetic grains in sediments proxies for the ratio of lithogenic to biogenic components controls on the detrital input of lithogenic material include eustasy and climate however induced and sea floor basin subsidence the development of an initial msec composite reference curve for the middle upper devonian of the anti atlas region of southern morocco is presented and discussed in the context of global sea level transgressive and regressive cycles msec trends composed of increasing ms magnitudes correlate well with episodes of regression whereas trends of decreasing ms magnitudes correlate with episodes of transgression