coupled oceanic oxygenation and metazoan diversification during the early middle cambrian the early middle cambrian fortunian to age 4 is characterized by a significant increase in metazoan diversification furthermore this interval is marked by a prominent environmental and ecological expansion of arthropod and echinoderm rich biotas recent redox work has suggested that this shift occurred during stable or decreasing marine oxygen levels suggesting that these paleobiological and paleoecological transformations were decoupled from a redox control we tested this idea by conducting new paleoredox analyses on age 2 age 4 cambrian outer shelf jiuqunao wangjiaping slope wuhe geyi and basinal zhalagou sections of the south china craton multiple sections indicate that mid depth waters transitioned from anoxic conditions during cambrian age 2 to stable oxic conditions during cambrian age 4 these findings suggest a stepwise expansion of oxic waters from shallow to deep settings during the early middle cambrian consistent with a redox control of metazoan diversification and ecological expansion more broadly despite the surge in redox work over the past decade this study highlights the need for continued coupled redox and paleontological studies to directly test models about the links between the evolution of animals ecosystems and marine redox conditions

phases of soil erosion derived colluviation in the loess hills of south germany in south germany soil erosion is as old as farming and dates back to early neolithic times its sedimentary products form thick colluvial and alluvial sediment bodies in all drainage basins numerous local studies exist but the extrapolation of findings from local case studies to a regional scale has been problematic here a graphical approach is used for frequency analysis of existing data a frequency distribution for optical dates on colluvial sediments from the beginning of agriculture until 1200 ad was constructed by 1 representing the optical ages by gaussian distributions and 2 summing all the single curves the resulting graph clearly shows phases of increased colluviation during periods of stronger human impact a first significant increase occurred during the bronze age during the iron age roman period and at around 800 ad distinct maxima appear in the distribution and highest frequencies are present towards the end of the analysed period at around 1100 ad conclusions that can be drawn from such an approach are limited by sampling bias and other factors but for the analysed period and on a regional and long term scale colluviation seems to have been mainly triggered by intensity of land use climatic fluctuations are of only secondary importance rainfall events that were sufficiently erosive to produce colluvial sediments occurred throughout the agricultural periods the limiting factor for colluvium production was sensitivity of the landscape to erosion and this is a result of land use d 2002 elsevier science b v all rights reserved

holocene soil formation and soil erosion at a slope beneath the neolithic earthwork salzmunde saxony anhalt germany abstract phases of formation and erosion of holocene soils were reconstructed based on a sequence of buried soil horizons and colluvial layers at a lower slope section beneath the neolithic earthwork of salzmunde germany the chronology is based on eight radiocarbon ages of charcoal soil organic matter as well as on archaeological age estimations of embedded artefacts until ca 2200 bc a chernozemic a c soil developed in fluvially redeposited loess the occurrence of charcoal the darker colour and a shift of soil matrix radiocarbon age indicate an alteration of the upper part of the humus horizon probably related to anthropogenic activities at ca 2200 bc this soil was probably buried rapidly by a colluvial layer at ca 2200 bc until ca 900 ad a phase of less intensive land use with slope stability followed during this phase a pedogenetic alteration probably under forest cover in the watershed and the deposition area of the upper part of the loess the buried soil and the prehistoric sediment occurred formation of chernozem cambisol the upper part of a dated humic crotowina fill was involved in pedogenesis as well soil formation is indicated by changes in soil colour brown pedogenic iron clay content the mineral assemblage of the clay fraction and magnetic susceptibility during medieval times ca 900 1500 ad two colluvial layers with a cumulative thickness of about 1 m buried this soil the partial destruction of the archaeological remains at the plateau started at this time during modern times since 1500 ad the deposition of two colluvial layers of a cumulative thickness of about 1 m completed the sequence of holocene slope deposits the results imply that the chernozem at the site might have been altered by prehistoric land use and altered further into a chernozem cambisol during a phase of slope stability of about 3000 years between the bronze age and medieval times the detected brunification processes took place at unexpected high rates

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

development of gullies and sediment fans in last glacial areas on the example of the suwalki lakeland ne poland abstract the density of gully network in the suwalki lakeland northeastern poland with typical last glaciation relief is 0 2 km km2 on average and locally reaches 1 2 km km2 most gullies are isolated but sporadically they create dendritic patterns the larger gullies are developed along dellies bowl shaped dry valleys or melt out valleys the smaller and shorter gullies occur on the slopes of melt out depressions and tunnel valleys ages of peat covered by fans at the mouths of larger gullies indicate that gully erosion started between 3520 70 to 2240 100 bp two different units build the fans and infilled the gullies the older unit in the lower part of fans is up to 5 m thick contains sand and gravel that generally originated from the bottom and bank erosion of the gullies and resembles alluvium the younger unit about 2 3 m thick consists of colluvium the fans at the mouths of smaller and shorter gullies are mainly built of colluvium the maximal grain diameter in both units is similar which testifies to a similar intensity of extreme rainfalls the analysed sediments have different characteristics which indicate that the source material and depositional changes are linked to forest clearance and farmland expansion starting in the 7th century ad and continuing in the middle ages

environmental changes during the holocene climatic optimum in central europe human impact and natural causes abstract the priority programme changes of the geo biosphere aimed to reconstruct the environmental history of central europe with emphasis on the time interval from 9000 to 5500 cal bp time slice ii coinciding with the holocene climatic optimum during this period the onset of human activities such as settlement agriculture and animal husbandry caused environmental changes studies of different landscape units in germany were carried out to identify these anthropogenically induced changes and to distinguish them from natural effects on the environmental system the investigated archives included laminated lake sediments fluvial sediments colluvia and soils speleothems peat and coastal sediments the different archives were examined using refined research methods including a variety of sedimentary and geochemical analyses together with pollen analysis and dating methods for the establishment of a reliable chronology the results of the various research groups are summarised and critically discussed based on these results the climatic optimum can be subdivided into three periods 1 the early atlantic from 9000 to 7500 cal bp with negligible human impact and stable environmental conditions 2 the late atlantic during early and middle neolithic from 7500 to 6300 cal bp with pollen evidence for vegetation changes but only negligible changes detectable in other proxy records and 3 the late atlantic during the younger neolithic jungneolithikum after 6300 cal bp with human impact observed in many archives and proxy records especially in the pollen record but also in lacustrine and fluvial sediments during the whole climatic optimum natural causes such as minor shifts of temperature did not induce substantial environmental changes though some changes such as temporary droughts may have facilitated and amplified the observed human impact

radiocarbon dating of soil organic matter radiocarbon ages of soil organic matter are evaluated with a model which incorporates the dynamics of the14c content of soil organic matter measured14c ages of soil organic matter or its fractions are always younger than the true ages of soils due to continuous input of organic matter into soils differences in soil c dynamics due to climate or soil depth will result in significantly different14c signatures of soil organic matter for soils of the same age as a result the deviation of the measured14c age from the true age of soil formation could differ significantly among different soils or soil horizons our model calculations also suggest that14c ages of soil organic matter will eventually reach a steady state provided that no climatic or ecological perturbations occur once a soil or a soil horizon has reached a steady state 14c dating of soil organic matter will provide no useful information regarding the age of the soil however for soils in which steady state has not been reached it is possible to estimate the age of soil formation by modeling the measured14c contents of soil organic matter radiocarbon dating of buried soils could in general overestimate the true age of the burial by as much as the steady state age of the soil or soil horizon

assessing the utility of fe al and fe speciation to record water column redox conditions in carbonate rich sediments abstract geochemical proxies based on fe abundance fe al and fe speciation have been widely applied to marine sediments in order to unravel paleo depositional redox conditions though geological time to date however these fe proxies have only been calibrated in relation to modern and ancient fine grained siliciclastic marine sediments this clearly limits their use particularly in relation to carbonate rich sediments and rocks to address this we here explore the applicability of fe based redox proxies in carbonates through three approaches first we have compiled fe al data for modern marine sediments to investigate variability in fe enrichments as a function of carbonate content and depositional setting second we have expanded this approach with a compilation of new and existing fe speciation data for modern and ancient marine sediments deposited under oxic and euxinic anoxic sulfidic water column conditions finally we show new data from paired limestone and dolomite sample sets to demonstrate the potential significance of deep burial dolomitization on the fe speciation redox proxy modern marine sediments deposited under oxic conditions show no relationship between fe al and carbonate content these sediments have an average fe al ratio of 0 55 0 11 with some higher values potentially being attributable to steady state early diagenetic remobilization of fe towards the sediment water interface in contrast significant fe al enrichments occur as a consequence of water column fe mineral formation and deposition either under anoxic conditions or due to input of anoxic hydrothermal fluids into oxic seawater iron speciation data also show no direct correlation with carbonate content and instead three groups can be distinguished based on total fe fe t and organic c contents sediments deposited under oxic water column conditions with fe t 0 5 wt generally plot below the lower fe hr fe t siliciclastic reference threshold 0 38 for distinguishing anoxic environments regardless of carbonate content also consistent with siliciclastic calibrations carbonate rich sediments deposited under anoxic water column conditions tend to have fe hr fe t ratios 0 38 in contrast oxic carbonate rich sediments with low fe t hr fe t ratios suggesting that the use of fe speciation for such samples is not appropriate for evaluating water column redox conditions taken together our data suggest that an fe t content of 0 5 wt rather than carbonate content represents the most suitable basis for identifying whether carbonate rich sediments are appropriate for fe based redox proxy analyses analysis of burial dolostones suggests that the fe speciation proxy may also be compromised by deep burial dolomitization where there has been a source of mobile fe to enrich rocks during recrystallization however pre screening can identify such samples this new assessment expands the utility of fe based redox proxies to also incorporate appropriate carbonate rich rocks provided that care is taken to assess the possible impact of deep burial dolomitization

glacial origin of the cryogenian nantuo formation in eastern shennongjia area south china implications for macroalgal survival abstract the cryogenian period was characterized by global glaciations imposing extreme environmental stresses on early multicellular organisms globally distributed diamictite deposits are the major evidence for these glaciation events but the glacial origin of at least some of these diamictite deposits has been disputed complicating interpretations of the environmental conditions influencing the evolution of life in the cryogenian 720 635 ma in this study we conducted a systematic sedimentological investigation of the marinoan age 650 635 ma nantuo formation in six sections representing a 20 km long east west transect in the eastern shennongjia area of south china the nantuo formation which ranges in thickness from 2 m in the east to 300 m in the west comprises diamictite conglomerate lonestone bearing sandstone green siltstone and black shale facies the eastern sections e g longxi and wushanhu consist mainly of diamictite facies exhibiting micro scaled rotation structures microshear grain stacking grain to grain contacts and water escape structures supporting their deposition in a subglacial setting in contrast the western sections shijiahe liziping and songluo consist of massive and graded diamictite and conglomerate facies consistent with an origin as glacially induced submarine debris flows furthermore the lonestone bearing sandstone facies in these sections contain abundant dropstones and mud pellets within finely laminated turbidites indicating an ice rafted origin with locally reworking by turbidity currents the green siltstone and black shale facies lack glacigenic features and may represent late deglacial deposits based on thickness and facies variations among the study sections we infer that the nantuo formation records glacial sedimentation on a complex paleotopographic surface that was incised into the underlying bedrock with subglacial deposits to the east transitioning into glaciomarine deposits to the west of study area the distal songluo section likely records three cycles of glacial advance and retreat in the form of a facies alternation between diamictite and black shale consistent with a dynamically fluctuating ice margin in summary our sedimentological investigation supports a glacial origin for the nantuo formation in the eastern shennongjia area the occurrence of the benthic macroalgal dominated songluo biota in the black shale facies at songluo suggests that strong glacial retreats provided niches for macroalgal survival in the cryogenian glacial ocean

development of a sequential extraction procedure for iron implications for iron partitioning in continentally derived particulates abstract the development of a sequential extraction procedure for iron in modern and ancient sediments is presented the scheme recognizes seven operationally derived iron pools 1 carbonate associated fe fe carb including siderite and ankerite 2 easily reducible oxides fe ox1 including ferrihydrite and lepidocrocite 3 reducible oxides fe ox2 including goethite hematite and akaganeite 4 magnetite fe mag 5 poorly reactive sheet silicate fe fe prs 6 pyrite fe fe py and 7 unreactive silicate fe fe u as such this is the first extraction scheme specifically developed to allow the separate identification of magnetite and the first to allow a complete evaluation of fe carbonate phases such as siderite and ankerite the scheme was developed following tests on pure mineral phases to evaluate the minerals solubilized by each technique and to determine optimum extraction times further tests on mixtures of pure minerals and on grain size separated sediments from two major us rivers and two glacial meltwaters validate the specificity of the scheme for different pools of iron minerals and demonstrate a high degree of reproducibility for each analytical stage the data obtained for the riverine and glacial sediments are additionally discussed in relation to the dominant modes of transport of different iron minerals in fine grained continental sediments

high resolution gully erosion and sedimentation processes and land use changes since the bronze age and future trajectories in the kazimierz dolny area naleczow plateau se poland abstract this paper presents the results of 40 years of research on the gully system in the doly podmularskie catchment 0 35 km in size which is situated in the south western part of the loess covered naleczow plateau in se poland topographic stratigraphic and pedologic investigations and monitoring of a tributary gully gully area 0 7 ha catchment 2 5 ha were combined with historical archaeological and palaeoecological records the results reveal a long and complex history in terms of the temporal and spatial extent and the impact of land use on gully erosion and the long term feed back mechanisms between land use changes and natural processes since the end of the pleistocene phases of gully erosion and subsequent filling occurred in the bronze age and around the 10th to 11th centuries the most severe deepening and expansion of the gully took place in the 17th century the results also show that field structures and land use intensity had a significant influence on the frequency and magnitude of run off soil erosion piping and landslide events the last significant erosion phase started in the mid 19th century with renewed headward retreat and down cutting within older gully fills today most of the catchment is either forested or the land is covered in berry shrubs in the future the area will continue to produce sediments because of the steep slopes and because there are still areas of bare soil with a low resistance to erosion a legacy from past land uses which will remain a factor affecting soil erosion and sedimentation processes in the future this study is an example of how important it is to observe and understand slow geomorphologic processes and rare extreme events in the light of land use changes when investigating long term human environment interactions

are mid latitude slopes sensitive to climatic oscillations implications from an early holocene sequence of slope deposits and buried soils from eastern germany abstract on a straight slope within the lake catchment of kleiner tornowsee brandenburg germany a sequence of slope sediments has been deposited during the late glacial the early holocene and around cal 4 2 ka before today 800 500 and 300 years ago the chronology is based on 21 radiocarbon dates and 11 osl dates and a deposition model including the numerical data as well as stratigraphic information has been calculated with oxcal 4 1 a comparison of the woody taxa of charcoal particles n 566 embedded within the sediments with the known regional vegetation history confirmed the reliability of the dates according to the age volume and distribution the deposition of the early holocene sediments at ca 10 3 kyrs ca 9 5 kyrs and ca 8 2 to 7 7 kyrs before today strongly suggests an influence of known climatic deteriorations phases on geomorphologic processes cold and dry climatic conditions probably promoted wildfires in pinus dominated forests and therefore triggered the observed repeated slope instability in consequence mid latitude slope deposits provide a potential to reconstruct the geomorphological response to climatic events at a high spatial resolution in contrast the recorded mid to late holocene soil erosion phases on the slope have been triggered by land use activities apart from traditional environmental archives slope deposits provide valuable information about the vegetation and climate history

diachronous cooling along the mogok metamorphic belt shan scarp myanmar the trace of the northward migration of the indian syntaxis abstract we present new observations and new mineral ages eight by the 40 ar 39 ar and nine by the 40 k 40 ar methods from high grade metamorphic and foliated intrusive rocks collected along the mogok metamorphic belt of central myanmar that complete preliminary results we previously published all 30 ages presented here confirm the oligocene to middle miocene age of the mogok metamorphism moreover the ages are young from the gulf of martaban in the south to the china myanmar border in the north showing a clear diachronism these results confirm a northward migration of the tectonic event responsible for the cooling of our samples at a velocity similar to the india relative to indochina velocity at the same period in addition intensive field work along a 800 km long section of the mogok metamorphic belt has revealed the numerous ductile structures that resulted from a strong nnw sse trending extension from the analogy between the present day local extrusion around the eastern indian syntaxis and the extension observed along the mogok metamorphic belt and from the diachronism we document we suggest that the central part of myanmar has recorded the northward passage of the eastern indian syntaxis with respect to indochina from oligocene to middle miocene

reconstructing rates and patterns of colluvial soil redistribution in agrarian hummocky landscapes humans have triggered or accelerated erosion processes since prehistoric times through agricultural practices optically stimulated luminescence osl is widely used to quantify phases and rates of the corresponding landscape change by measuring the last moment of daylight exposure of sediments however natural and anthropogenic mixing processes such as bioturbation and tillage complicate the use of osl as grains of different depositional ages become mixed and grains become exposed to light even long after the depositional event of interest instead osl determines the stabilization age indicating when sediments were buried below the active mixing zone these stabilization ages can cause systematic underestimation when calculating deposition rates our focus is on colluvial deposition in a kettle hole in the uckermark region northeastern germany we took 32 samples from five locations in the colluvium filling the kettle hole to study both spatial and temporal patterns in colluviation we combined osl dating with advanced age modelling to determine the stabilization age of colluvial sediments these ages were combined with an archaeological reconstruction of historical ploughing depths to derive the levels of the soil surface at the moment of stabilization the deposition depths which were then used to calculate unbiased deposition rates we identified two phases of colluvial deposition the oldest deposits 5 ka were located at the fringe of the kettle hole and accumulated relatively slowly whereas the youngest deposits 0 3 ka rapidly filled the central kettle hole with rates of two orders of magnitude higher we suggest that the latter phase is related to artificial drainage facilitating accessibility in the central depression for agricultural practices our results show the need for numerical dating techniques that take archaeological and soil geomorphological information into account to identify spatiotemporal patterns of landscape change and to correctly interpret landscape dynamics in anthropogenically influenced hilly landscapes

kinematics of the tengchong terrane in se tibet from the late eocene to early miocene insights from coeval mid crustal detachments and strike slip shear zones abstract it is generally believed that the extrusion of se tibet was bounded by the dextral gaoligong and the sinistral ailaoshan red river strike slip shear zones from the oligocene to early miocene this study integrates field mapping structural analysis and geochronology in western yunnan china where foliated precambrian basement rocks and late cretaceous to early eocene plutons are exposed to the west of the gaoligong shear zone we found that late eocene to early miocene flat lying ductile shear zones were kinematically related to steeply dipping strike slip shear zones four elongated gneiss domes donghe guyong yingjiang and sudian are cored by high grade metamorphic rocks and pre kinematic granite plutons and bounded by top to ne detachments and ne trending dextral strike slip shear zones zircon u pb ages from la icp ms analysis and 40 ar 39 ar ages of micas and hornblende demonstrate that the flat lying donghe detachment 35 15 ma and the nabang dextral strike slip shear zone 41 19 ma were sites of prolonged mostly coeval ductile deformation from amphibolite to greenschist facies metamorphism the gaoligong shear zone experienced dextral shearing under similar metamorphic conditions between 32 and 10 ma consistent 40 ar 39 ar ages of hornblende from the three shear zones indicate their contemporaneity at mid crustal depth causing the rapid exhumation and sw ward extrusion of the tengchong terrane the strain geometry and shear zone kinematics in the tengchong terrane are interpreted with folding of the anisotropic lithosphere around a vertical axis i e the northeast corner of the indian plate since 41 ma the newly discovered ne trending sudian yingjiang and lianghe strike slip shear zones are subordinate ductile faults accommodating the initially rapid clockwise rotation of the tengchong terrane the detachments caused mid crustal decoupling and faster sw ward extrusion below the sedimentary cover whereas the strike slip shear zones accommodated extrusion and clockwise rotation of the tengchong terrane around the proto eastern himalayan syntaxis since the late eocene

prehistoric and roman gullying in the european oess belt a case study from central belgium in contrast with the understanding of present day soil erosion processes knowledge on past soil erosion phenomena is still rather limited although some studies report on severe gully erosion phases during the fourteenth and eighteenth centuries almost no evidence is available that documents earlier gully erosion phases this study investigates the development and age of two old permanent gullies that are conserved in the ancient meerdaal forest in central belgium the development history of both gullies is very similar in the first gully archaeological evidence was found indicating an erosion phase during roman times followed by a partial infilling of the gully in the second gully radiocarbon dating provided evidence of the same roman activity phase cal yr 46 bc ad 78 but also of an earlier incision phase during the middle bronze age cal yr 1743 1602 1568 1533 bc also here the erosion phase was followed by a partial infilling this limited infilling indicates that the catchment of the gullies was reforested quite rapidly hereby cutting off all runoff and sediment production this has led to a unique situation in the meerdaal forest with the conservation of about 43 similar large gullies in an area of about 17 km 2 this area has a high geovalue as the studied gullies are among the oldest and best conserved gullies in northwestern europe

the use of operationally defined sequential fe extraction methods for mineralogical applications a cautionary tale from mossbauer spectroscopy abstract reactive iron minerals are crucial components of global nutrient cycles directly controlling carbon transport and storage in marine sediments sequential selective extraction is frequently used for quantitatively characterising and chemically isolating individual fe mineral phases reagent specific mineral solubility is fundamental to the success of any sequential extraction but is strongly affected by the varying physical and chemical morphology intrinsic to natural mineral samples natural sediment rock and soil samples often contain a mineral mixture which further modifies solvent efficacy 57fe mossbauer spectroscopy only probes the hyperfine interactions between next nearest neighbouring atomic nuclei in the crystal lattice and is less affected by variation in mineral grain size and crystallinity than conventional x ray based methods in this study we used mossbauer spectroscopy in a novel context to cross calibrate and optimise a popular but frequently misused sequential fe extraction protocol our results showed that incomplete and premature removal of the target fe minerals could occur at nearly every stage of the extraction and in many cases the leachate fe content did not represent the target phase at all crystalline natural siderite and amorphous synthetic goethite were detected in the mossbauer spectrum of the ammonium oxalate extraction for magnetite after which all reactive fe minerals should have been removed consistent with previous studies and unlike many other clay minerals nontronite was extracted as part of the highly reactive fe pool and in fact our data indicate that this mineral was extracted by the initial na acetate extraction that targets carbonate bound fe matrix effects appeared to cause variable yield efficiencies synthetic goethite was successfully removed when present as an individual mineral yet persisted beyond its target extraction when present in an fe mineral mixture although suitable for the quantification of operationally defined fe pools we caution the unverified use of sequential fe extraction protocols for mineral specific applications the application of sequential fe extractions to define the reactive fe pools as a paleoredox proxy of depositional conditions appears relatively robust the premature removal of 2 line ferrihydrite observed in this study due to the use of the more aggressive na acetate extraction for crystalline siderite does not limit the quantitative use of the sequential fe extraction in ancient sediments where such easily reducible oxides are unlikely to persist in contrast attributing the outcomes of operationally defined fe pools to specific fe minerals is precarious and potentially entirely erroneous where fe mineral specificity or separation is required we recommend post extraction validation by another secondary technique mossbauer spectroscopy offers such a method that can independently verify extraction stages and assess mineral specificity

grain size of the overbank deposits as carriers of paleogeographical information abstract overbank deposits of the vistula river and its tributaries were deposited during the whole late glacial and the holocene but at various rates they are differentiated with respect to the grain composition that corresponds to climatic vegetation changes at the turn of the late glacial and the holocene to anthropogenic deforestation in the neoholocene and to the distance from an active channel

origin and evolution of closed depressions in central belgium european loess belt closed depressions cds are lower lying areas where the sediment eroded from the surrounding soil surfaces draining towards the cd is trapped in the system cds have been reported in several regions of the european loess belt and are attributed either to natural processes e g dissolution of subsurface horizons or to human intervention e g quarrying previous studies focussed mainly on cropland areas where however only few and largely filled in cds remain the objectives of this study were to i assess the spatial distribution of cds under forest and cropland ii to determine and compare the morphology of cds under forest and under cropland and iii to determine the origin and age of these cds under forest in a study area located partly in ancient forest 13 km2 and partly in cropland 29 km2 a systematic survey revealed the presence of 71 cds under forest 5 3 cd km 2 and 30 cds under cropland 1 cd km 2 comparison of their morphology showed that cds under forest were significantly deeper with steeper sidewalls and a smaller surface area because of the erosion and deposition processes acting on the cds under cropland by comparing cds that had been under cropland for different time intervals the rate of this morphological evolution could be reconstructed analysis of the soil stratigraphy of two representative cds in the ancient forest area confirmed their origin as quarries most probably calcareous loess was excavated since this soil horizon about two to five meters thick was completely absent within the cds dating of the infilling of one cd by optically stimulated luminescence osl shows that the cd filled in between the first century bc and the fourth century ad this dating corresponds to the dating of sediment deposits in nearby human induced gullies that were attributed to an agricultural land use phase between the 18th century bc and the third century ad

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

holocene evolution of closed depressions and its relation to landscape dynamics in the loess areas of poland past pleistocene topography of the loess uplands is rich in local sinks closed depressions cds influencing sediment fluxes soil sediment sequences from cds constituting geoarchives where lands

change in the frequency of extreme events as the indicator of climatic change in the holocene in fluvial systems abstract the transformation of natural systems of climatic origin in the holocene may be realised by a change in the type of extreme events or by a change in their frequency or by both the rapid warming at the younger dryas preboreal transition exemplifies a parallel drop in frequency and a change in the type of events several wetter phases of the holocene are characterised by rises in frequency of various types of extreme rainfalls the fragmentary records of events in the fluvial and slope systems coincide with smoothed variations in stable ecosystems and shifts of ecotonal zones such as tree line and lake levels

the impact of natural and anthropogenic processes on the evolution of closed depressions in loess areas a multi proxy case study from naleczow plateau eastern poland abstract closed depressions are reported in loess landscapes in various parts of europe the anthropogenic and natural origin of closed depressions is highly debated in literature closed depressions are an important component of the landscape in loess areas of the lublin upland furthermore they perform the role of local closed sediment basins creating unique conditions for the preservation of soils and colluvial sediments along with the record of the evolution of the holocene landscape occurring under the influence of climate changes and human activity the study objective was to evaluate the contribution of natural and anthropogenic processes influencing the origin and evolution of closed depressions the naleczow plateau is composed of loess whose thickness varies from a few meters to 30 m 1761 closed depressions have been documented within the naleczow plateau 493 km 2 a detailed investigation was conducted within selected closed depression dissected by a deep and long road trench the studied form was 40 m long 26 m wide and 0 7 m deep the analyzed exposure 20 m long and 7 m high presents a cross section of the closed depression fieldwork and subsequent laboratory analyses were conducted morphological micromorphological microstructural geochemical physico chemical osl and 14 c dating archaeological and historical correlations were also performed the primary bottom and slopes of the studied depression are composed of loess in situ overlain by late glacial holocene fossil soil periglacial structures such as deformed ice wedge pseudomorphs cracks and lenses macro structures were documented in the loess and palaeosol at the bottom of the closed depression the depression is filled with neoholocene soil sediment sequences consisting of 2 layers of colluvial sediments separated by neoholocene subfossil soil they constitute a record of the two stages of cd infillings in the holocene connected with human agricultural activity lasting from the neolithic up to modern times a detailed analysis of the loess late glacial holocene fossil soil and holocene colluvial sediments made it possible to distinguish the stages of evolution of closed depression influenced by changing environmental conditions and human activity during the late glacial and holocene

age and source of colluvial sediments at vaihingen enz germany abstract colluvial sediments accumulated on the lower slopes of a ridge as a result of past and present soil erosion were dated by optical 14 c and archaeological methods this allowed us to reconstruct the depositional history of the colluvium and also to identify temporary sedimentary sinks in its transportational pathway a cascade model of colluvium formation is developed colluvial sediments resulting from early soil erosion in the neolithic to iron age periods were mainly deposited on the upper slopes significant deposition on the lower slope occurred for the first time during the iron age and roman period since then deposition rates have increased because of more intensive land use

slope deposits as an indicator of anthropopressure in the light of research in central poland abstract results of research on neo holocene slope covers uncovered at archaeological sites in central poland are described in this paper geoarchaeological investigations have been undertaken in the ner river basin distinctive archaeological relicts of human activity document periods of intensive activity of human societies artefacts included within deposits play a very important role in correct recognition of the chronology of covers and ecofacts for reconstructions of environmental evolution the origin and development of slope covers have been correlated with anthropogenic changes of the natural environment two main phases of acceleration of slope processes have been recognised dated to the middle bronze age and to the late roman period slope deposits have been classified as deluvia deluvial slope wash deposits or colluvial deposits their features are most typical for deluvial sands and if they contain more humic matter for soil deluvia the deluvial covers have been deposited as an effect of moderately intensive slope wash processes accumulation of slope deposits has resulted from natural processes initiated by human impact during periods of intensive settlement and economic activity the slope cover sediments are the source for recognition of intensity of human impact and of economic activity of ancient societies and for distinct phases of hiatuses of settlement development the possibility of archaeological and palaeogeographical interpretations based on research on slope covers at archaeological sites is presented

a model for iron deposition to euxinic black sea sediments sulfur isotope and c s fe elemental data from the lower devonian siegenian emsian hunsruck slate of germany allow the conditions that led to the pyritization of soft bodied fossils to be determined the slates preserving pyritized soft tissues generally contain low concentrations of organic matter 0 3 0 4 percent c and pyrite sulfur 0 0 2 percent s respectively but are unusually rich in total and hcl extractable iron concentrations of iron are significantly lower in samples of the hunsruck slate from areas where fossils lack pyritized soft tissues the fossil pyrite is very enriched in s 34 compared to fine grained disseminated pyrite in the adjacent slates delta fossil sediment 10 to 50 permil suggesting that pyritization of the fossils persisted into later stages of authigenic mineralization pyrite formation in the sediments was limited by the low concentrations of metabolisable organic matter leaving residual sulfate and iron available for continued fossil pyritization in organic rich microenvironments a diffusion with precipitation model indicates that a critical control on the initial preservation of readily metabolisable soft tissue in this way is the presence of high concentrations of sediment iron capable of being solubilized during shallow burial diagenesis in association with low concentrations of metabolisable organic matter in the matrix pore waters rich in dissolved iron allow the sulfide generated by the decay of readily metabolisable soft tissue to be trapped efficiently within the carcass

mechanisms of mass and heat transport during barrovian metamorphism a discussion based on field evidence from the central alps switzerland northern italy 1 tectonic and metamorphic data for the central alps switzerland italy are used to discuss this classic example of a barrovian metamorphic terrain notably the evolution of its thermal structure in space and time available p t t data indicate variable contributions of advective and conductive heat transport during collision and subsequent cooling and exhumation some areas experienced a prolonged period of partial melting while other areas at the same time show but moderate heating the barrow type metamorphic field gradient observed in the final orogen is the result of two distinct tectonic processes with their related advective and conductive heat transport processes the two tectonic processes are 1 accretion of material within a subduction channel related to decompression and emplacement of high pressure units in the middle crust and 2 wedging and related nappe formation in the continental lower plate the second process postdates the first one wedging and underthrusting of continental lower plate material produces heat input into lower crustal levels and this process is responsible for predominantly conductive heat transport in the overlying units the interacting processes lead to different maximum temperatures at different times producing the final barrovian metamorphic field gradient the south experienced rapid cooling whereas the north shows moderate cooling rates this discrepancy principally reflects differences in the temperature distribution in the deeper crust prior to cooling differences in the local thermal gradient that prevailed before the cooling also determined the relationships between cooling rate and exhumation rate in the different areas citation berger a s m schmid m engi r bousquet and m wiederkehr 2011 mechanisms of mass and heat transport during barrovian metamorphism a discussion based on field evidence from the central alps switzerland northern italy tectonics 30 tc1007 doi 10 1029 2009tc002622

cenozoic clockwise rotation of the tengchong block southeastern tibetan plateau a paleomagnetic and geochronologic study abstract paleomagnetic data from 50 35 ma likely 40 ma mafic dykes in yunnan southeastern tibetan plateau cutting 115 ma granitoids record the rotation of the tengchong lhasa block around the east himalayan syntaxis ehs ti rich titanomagnetite and magnetite carry a primary magnetic component group1 a magnetic overprint resides in magnetite group2 likely induced by low grade metamorphism between 30 and 10 ma the tilt corrected overall mean directions are d i 89 8 35 1 for group1 and d i 33 3 41 4 for group2 these data imply a clockwise rotation of 87 87 3 12 5 of the tengchong block since remanence acquisition at 40 ma with respect to stable eurasia the average rotation rate of 2 18 0 31 myr is at the upper limit of the present day rotation rates around the ehs obtained from gps velocities and quaternary strain rates the remagnetized group2 indicates a poorly defined rotation of 31 31 2 32 9 our key results the detection of 87 clockwise rotation with high rotation rates following the india asia collision and a decrease in rotation rates during the miocene suggest that first the tengchong block rotated rapidly around the ehs synchronous with eastward tectonic escape of lithospheric blocks the later slower clockwise rotation similar to those recorded geodetically may be related to viscous flow of tibetan crust

a critical look at iron paleoredox proxies new insights from modern euxinic marine basins enrichments in reactive iron occur under euxinic marine conditions that is where dissolved sulfide is present in the water column these enrichments result primarily from the export of remobilized iron from the oxic shelf which is scavenged from the euxinic water column during syngenetic pyrite formation and deposited in the underlying sediments strongly elevated ratios of highly reactive iron to total iron fehr fet and total iron to aluminum fet al and high degrees of pyritization dop are each products of this enrichment process these paleoredox proxies are among the most faithful recorders of ancient euxinia contrary to previous arguments iron enrichment is decoupled from biogenic sediment inputs but it does appear to be a uniquely euxinic phenomenon in other words we can rule out a major contribution from preferential physical transport of fehr rich detrital sediment to the deep basin which could also operate under oxic conditions furthermore enrichment via the shuttling of iron remobilized from oxic shelves appears to be limited by inefficient transport and trapping processes in deep oxic basins elevated fet al ratios in the euxinic sediments also cannot be a product of internal enhancement of the reactivity of the detrital iron pool without net fehr addition these conclusions are supported by observations in the modern black sea orca basin and effingham inlet fet al ratios are unambiguous recorders of paleoredox even in sediments that have experienced high degrees of metamorphic alteration however this study suggests that high siliciclastic accumulation rates can swamp the enrichment mechanism resulting in only intermediate dop values for euxinic sediments and fet al ratios that mimic the oxic shelf such dilution effects are well expressed in black sea basinal turbidites and rapidly accumulating muds on euxinic basin margins under conditions of persistent euxinia varying extents of fehr enrichment can illuminate spatial and temporal gradients in siliciclastic sedimentation the magnitude of enrichment is a function of the source shelf to sink ocean basin areal ratio suggesting that iron proxies can also record ocean scale paleoenvironmental properties through muted enrichments at times of very widespread euxinia for the first time manganese data are interpreted in light of the redox shuttle model as for the iron data the black sea orca basin and effingham inlet show enrichments in total manganese in the deep euxinic basin suggesting export from the suboxic porewaters of the oxic shelf and scavenging and burial in the basin the black sea data reveal iron and manganese enrichment across the broad deep euxinic basin suggesting efficient lateral transport and deep water mixing tied to the physical properties of the water column

historical soil erosion by water in germany scales and archives chronology research perspectives abstract the published record of historical soil erosion by water in germany as deduced from dated slope deposits n 306 alluvial sediments n 120 and lake sediments is summarized in this paper the number of sediments investigated reflects the state of knowledge chronology of historical soil erosion and to a certain degree the intensity of the human impact on german landscapes during the holocene even though few data of calculated historical soil erosion intensities exist an estimation of historical soil erosion in germany combining the available data has been calculated soil erosion in germany occurred first locally during the early holocene probably triggered by climatic variability from the neolithic onward the record reflects the human impact according to agricultural land use the observed variability indicates phases of weaker and regained intensity of agricultural land use in germany few records characterise the early and middle bronze age ca 2000 1600 bc and the migration period and the early medieval times ca 400 1000 ad surprisingly for the roman emperor times ca 1 400 ad a decreasing number of soil sediments is recorded even when the data from southern germany is examined separately phases characterised by an increase in soil erosion were the late bronze age and pre roman iron age ca 1600 bc 1 ad the high and late medieval times ca 1000 1350 ad and the modern times ca 1500 ad until today some extraordinary heavy precipitation events late 18th early 19th first half of 14th century pre roman iron age topped the even high soil erosion intensities research gaps as well as potential for future research as derived from the available data are outlined

geochronological constraint on the cambrian chengjiang biota south china the cambrian chengjiang biota of south china provides compelling fossil evidence for the rapid appearance of metazoan phyla in earth history the cambrian explosion however the timing of the chengjiang biota is poorly constrained owing to lack of datable rock materials within the maotianshan shale that yields the fossils here we integrate secondary ion mass spectrometry sims and chemical ablation isotope dilution thermal ionization mass spectrometry ca id tims u pb analyses of detrital zircons from the maotianshan shale to provide high precision geochronological constraint on the chengjiang biota the youngest group of sims u pb detrital zircon dates yields an age peak at 520 ma six zircons from this group are further dated by the ca id tims u pb technique but suggesting that they were not formed from a single zircon growth event thereby neither the age peak nor the weighted mean age defined by the youngest sims u pb dates could represent the maximum depositional age of the maotianshan shale instead the youngest ca id tims u pb date 518 03 0 69 0 71 ma 2 analytical uncertainty incorporates u pb tracer calibration uncertainty provides the first robust maximum age of the chengjiang biota this new geochronological constraint on the chengjiang biota indicates that the cambrian explosion reached its major phase around 518 03 0 69 0 71 ma demonstrating a protracted process 22 myr for the cambrian explosion supplementary material sims and ca id tims zircon u pb data are available at https doi org 10 6084 m9 figshare c 4024849

early cambrian oxygen minimum zone like conditions at chengjiang the early cambrian succession at chengjiang contains the most diverse cambrian fossil assemblage yet described and contributes significantly to our understanding of the diversification of metazoans in the cambrian explosion the cambrian period occupies a transitional episode of global ocean chemistry following the oxygenation of the surface ocean and of shallow marine environments during the ediacaran period but prior to the establishment of a predominantly oxygenated deep ocean in the mid paleozoic despite recent attention a detailed understanding of the chemical conditions that prevailed in early cambrian marine settings and the relationship of those conditions to early metazoan ecosystems is still emerging here we report multi proxy geochemical data from two drill cores through the early cambrian series 2 yu anshan formation of yunnan china results reveal dynamic water column chemistry within the succession which progressively shifted from euxinic to oxic conditions during deposition of the yu anshan formation the chengjiang biota occurs in strata that appear to have been deposited under an oxygen depleted water column that may have supported denitrification as in modern oxygen minimum zones the oxygenated benthic environments in which the chengjiang biota thrived were proximal to but sharply separated from the open ocean by a persistent anoxic water mass that occupied a portion of the outer shelf oxygen depletion in the lower water column developed dynamically in response to nutrient availability and possibly at lower thresholds of productivity due to lower atmospheric oxygen concentrations in cambrian these findings suggest that the frequent development of oxygen limiting conditions in continental margin settings provided an environmental barrier that may have affected biogeographic ecological and evolutionary development of early metazoan communities

differential proxy responses to late allerod and early younger dryas climatic change recorded in varved sediments of the trzechowskie palaeolake in northern poland abstract high resolution biological proxies pollen macrofossils cladocera and diatoms geochemical data xrf element scans toc c n ratios 18 o carb and 13 c org values and a robust chronology based on varve counting ams 14 c dating and tephrochronology were applied to reconstruct lake system responses to rapid climatic and environmental changes of the trzechowskie palaeolake trz northern poland during the late allerod younger dryas yd transition palaeoecological and geochemical data at 5 15 years temporal resolution allowed tracing the dynamics of short term shifts of the ecosystem triggered by abrupt climate change the robust age control together with the high resolution sampling allowed the detection of leads and lags between different proxies to the climate shift at the allerod younger dryas transition our results indicate 1 a water level decrease and an increase in wind activities during the late allerod and the allerod yd transition which caused intensified erosion in the catchment 2 a two decades delayed vegetation response in comparison to the lake depositional system comparison with the lake meerfelder maar record revealed slightly different vegetation responses of the trzechowskie palaeolake at the yd onset

temporal variations in runoff and sediment yield associated with soil surface roughness under different rainfall patterns abstract soil surface roughness ssr is one of the topographic factors affecting soil erosion currently temporal variation characteristics of runoff and sediment yield of ssr is still unknown in this study ridge tillage rt and linear slope ck were used to simulate different ssr artificial rainfall experiments including increased and decreased rainfall series were conducted in two runoff plots on a slope gradient of 15 the rainfall intensities were 1 0 1 5 and 2 0 mm min 1 and the rainfall duration were 60 40 and 30 min respectively a method combining of the pin meter and photography was used to measure micro topographic changes before and after each run the results showed that the ssr values of rt ranged from 175 94 mm to 181 50 mm and ssr values of ck ranged from 75 66 mm to 79 80 mm the temporal variations of runoff and sediment yield associated with ssr had positive long range correlation and varied periodically every 9 16 min under different rainfall patterns there was a critical value on the spatial heterogeneity of ssr that affecting soil erosion ssr reduced the frequency of periodic oscillations of runoff and sediment yield and then reduced the turbulence of runoff and sediment yield during the rainfall which had good effect of soil and water conservation when ssr exceeded the certain critical condition ssr served as the source of erosion by increasing the periodic oscillation energy increased the turbulence of runoff and sediment yield which led to a large amount of soil and water loss the findings will help elucidate soil erosion mechanisms in sloping farmland and provide a new insight for understanding of temporal variations in runoff and sediment yield

a burgess shale like fauna from the lower cambrian of north greenland the cambrian explosion refers to the major adaptive radiation of the metazoans during the earliest phanerozoic an event that is best known by the abrupt appearance of hard parts near to the precambrian cambrian boundary 550 myr bp 1 deciphering this important evolutionary episode depends largely on the study of these skeletal remains2 3 together with trace fossils that include burrows and trackways4 5 many of these latter fossils evidently represent the activities of soft bodied organisms such as worms and lightly sclerotized arthropods whose exact identity is seldom known not least because they can be fossilized only in exceptional circumstances6 however documenting the soft bodied representatives of early metazoan communities cannot be neglected if they accounted for a substantial fraction of these early biotas7 here we report a new soft bodied fauna from the lower cambrian of north greenland this assemblage has highly significant similarities with the younger burgess shale and provides additional evidence for the geological longevity of this faunal type and its widespread distribution in deeper waters of cambrian oceans

closed depressions in the european loess belt natural or anthropogenic origin abstract closed depressions cds are typical geomorphological features of the loess belt in europe cds have been reported in several regions of the european loess belt where they are described as hollows mardeles wymoki crovuri bludtsa and zapadiny the natural and anthropogenic origins of cds are debated in literature moreover no comprehensive review of the geomorphic properties or the evolution of these depressions exists therefore this paper reviews the characteristics of cds in the european loess belt and attempts to better understand their genesis based on detailed case studies the main morphometric features as well as sediment deposits within cds in several sub regions of europe were analysed and compared morphometric properties of cds from the west european and east european loess belt were investigated through a comparison of cds from two representative regions i e east poland and central belgium in both study areas cds under cropland are similar however a comparison of morphological features of cds under forest revealed clear differences suggesting a different origin of cds from both regions infilled sediments in cds show various litho genetical features in different regions of the european loess belt the morphometric features ages and stratigraphy of infillings clearly indicate that both anthropogenic and natural processes have shaped these landforms within the loess belt of europe cds observed in eastern europe may have a very different origin than those documented in western europe detailed analysis of cds in poland and in neighbouring regions of east europe suggest that cds are natural landforms thermokarst deflation and dissolution of loess are reported as probable genetic processes in contrast several studies in western europe indicate a dominant anthropogenic origin i e digging of calcareous loess or marls bomb and mining craters collapse of underground limestone quarries although cds formed by natural processes i e piping dissolution of limestone and salt lenses below the loess cover are reported as well cds act as important archives allowing one to reconstruct both natural and anthropogenic processes operating in the past as cds store most sediments eroded within their catchment they provide ideal sediment traps to assess long term erosion rates in these environments which have hitherto been under researched more research is needed to unravel the genesis and evolution of these depressions to better understand the importance of the late glacial and holocene stages for the morphogenesis of the loess belt in europe

test of thermoluminescence dating of buried soils from mt kenya kenya we have applied the partial bleach r gamma thermoluminescence tl dating method to four organic rich ab horizons of buried soils from mount kenya our objective was to test the feasibility of directly measuring the time of last exposure to sunlight of the fine grained silicate minerals within these horizons the resulting apparent ages for three samples of 1 2 0 3 6 2 and 10 2 ka 1 std dev are in general agreement with associated 14c age estimates from buried whole soil paleosol samples the fourth sample of an age though unknown presumed to lie beyond the 14c dating limit yielded a tl age estimate of 60 20 ka notwithstanding some limitations these results are encouraging and imply that with simple refinements this tl method is capable of directly dating accurately such buried soils probably to well beyond the 40 ka 14c dating limit

intra continental transpression and gneiss doming in an obliquely convergent regime in se asia abstract the tengchong terrane comprises a sequence of linear dome like zones cored by granite and migmatitic layers these cores are mantled by predominantly gneiss and subordinate schist sequences decreasing in deformation intensity outward from extensive mylonitization to weak mylonitization the pre doming deformation was characterized by the formation of large scale top to the east shearing d1 in the gneiss terrane locally preserved flat lying foliation s1 weak folding f1 and emplacement of the mangbang granite during the cretaceous 114 104 ma the second stage of deformation d2 consisted of map scale east verging folds f2 dome amplification and minor lateral strike slip shear zones between the anticlines in the gneiss and migmatitic sequences extensive partial melting and emplacement of 67 30 ma synkinematic granitoid bodies veins occurred leading to the emplacement of wedges of granite into the easterly directed f2 fold cores these wedges formed kilometer scale granitoid domes the post doming d3 deformation with transpression recorded strain partitioning with simple shear dominated high strain zones along the gaoligong and nabang dextral lateral strike slip shear zones active during 30 11 ma late transtensional deformation d4 during cooling of the entire terrane involved the localized low temperature gaoligong west and east detachment faults that controlled the late exhumation of the gaoligong metamorphic zone since 10 ma our structural observations combined with previous studies suggest that this style of doming is a representative type of intra continental deformation in the cenozoic during the oblique india asia collision the actual dome shapes reflect formation of antiforms during compression dominated transpression prior to localized strike slip shearing in the accommodation belt around the eastern himalayan syntaxis vertical exhumation of crustal material by contractional doming played an important role in absorbing the vast majority of the internal deformation of crustal fragments during oblique collision

trace element behavior and redox facies in core shales of upper pennsylvanian kansas type cyclothems the black shale submember of core shales of pennsylvanian kansas type cyclothems is highly enriched in redox sensitive trace elements tes relative to the overlying gray shale submember as well as to many other modern and ancient organic rich deposits controls on trace element behavior in the black shale can be inferred from trace element enrichment factors efs relative to gray shale and the relationship of tes to total organic carbon toc most tes conformed to one of two patterns 1 mo u v zn and pb exhibited moderate efs and strong covariation with toc in samples having 10 wt toc and 2 cu ni cr and co exhibited low efs and moderate to strong covariation with toc in all samples these patterns are inferred to represent different responses to benthic redox conditions the first pattern is characteristic of tes of strong euxinic affinity i e those taken up in solid solution by fe sulfide or involved in other reactions catalyzed by free h2s and resident mainly in authigenic phases whereas the second pattern is characteristic of tes of weak euxinic affinity i e those not strongly influenced by the presence of free h2s and resident mainly in the organic carbon or detrital fractions of the sediment these inferences allowed development of a multiproxy technique for assessing redox facies in black shale samples euxinic conditions were considered to have existed if at least two of four redox indicator trace elements mo u v zn showed euxinic levels of enrichment and nonsulfidic anoxic conditions were inferred otherwise the validity of the procedure is indicated by 1 agreement among all four redox indicators for a large majority of samples 69 of 185 2 among samples yielding a mixed redox signal a systematic sequence of te enrichment v zn mo u and 3 for tes of weak euxinic affinity reduced variance among samples representing each redox facies sequential enrichment may be a response to differential redox thresholds for accumulation e g v or postdepositional remobilization of trace elements e g u and may provide a basis for finer assessment of redox conditions in low oxygen paleoenvironments than permitted by simple classification schemes the multiproxy procedure for redox facies analysis developed in this study is likely to be more reliable than widely used single proxy indicators based on trace elements e g mo authigenic u or v v ni or c s fe systematics e g s toc or dop d 2004 elsevier b v all rights reserved

new u pb age from the basal niutitang formation in south china implications for diachronous development and condensation of stratigraphic units across the yangtze platform at the ediacaran cambrian transition abstract the black shale dominated niutitang formation covers a large portion of the early cambrian yangtze platform in south china the base of this unit has been traditionally taken as the ediacaran cambrian boundary ca 542 ma recent radiometric ages from the basal niutitang formation and its correlative units however are significantly younger than 542 ma and raise questions about the diachrony of stratigraphic units across the yangtze platform at the ediacaran cambrian transition here we report a new u pb sensitive high resolution ion microprobe shrimp age of 522 7 4 9 ma from a tuffaceous bed of the basal niutitang formation in a deep water section in taoying guizhou province of south china this age in combination with existing ages and biostratigraphic data suggests that the base of the niutitang formation is of tommotian or upper meishucunian age and the ediacaran cambrian boundary is most likely within the liuchapo formation the depositional age of the unusual metal enriched ni mo pge sulfide deposits which are approximately 1 m above the ca 523 ma tuffaceous bed should be early tommotian upper meishucunian rather than early nemakit daldynian lower meishucunian regional correlation confirms the diachronous development and condensation of stratigraphic units across the early cambrian yangtze platform and provides important information for understanding the paleogeography and paleoceanographic events at the ediacaran cambrian transition in south china

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

luminescence dating of hillslope deposits a review abstract luminescence dating determines the last exposure to light of quartz and feldspar mineral grains and thus the time a sediment was laid down prerequisite is that the sediment grains were sufficiently exposed to light prior to deposition for eolian deposits this seems a fair assumption although exceptions may well exist for other depositional environments light exposure prior to burial is often restricted in duration intensity and spectral composition and may result in an age overestimation recent developments now allow dating of sediments that were exposed to only little light prior to deposition the main developments are single aliquot techniques and statistical tests that allow extraction of valid age estimates even from deposits in which bleached and unbleached grains are mixed these developments in combination with the fact that the great majority of sediments near the earth s surface are not of eolian origin have resulted in the large interest in the luminescence dating of non eolian deposits here we review possibilities and challenges of luminescence dating of colluvial deposits we summarize techniques for the detection and handling of insufficiently bleached sediments a common condition in colluvial deposits we give an overview how luminescence dating has been applied on hillslope sediments for reconstructing landscape response to climate change to analyze past fault activity and unravel human induced soil erosion we discuss sampling strategies and give guidelines as to which techniques are best suited to establish luminescence chronologies for colluvium

deep water dissolved iron cycling and reservoir size across the ediacaran cambrian transition abstract the majority of the deep ocean was likely under ferruginous conditions during the first four billion years of earth s history as the atmosphere was gradually oxygenated the sources sinks redox cycling and reservoir size of dissolved iron in the deep ocean are likely to have changed dramatically whether deep water was thoroughly oxygenated by the time of the ediacaran cambrian transition and the relationship of this oxygenation to the cambrian explosion remains debated to explore the degree of oceanic oxygenation and its effect on cambrian explosion we measured the iron isotopic composition 56fe of bulk rock i e cherts and mudstones shales through the piyuancun and hetang formations using samples collected from the chunye 1 core on the lower yangtze block in western zhejiang the limited variation in 56fe values 0 55 during the end ediacaran and cambrian stages 1 3 to

past and present interaction between the catchment and the valley floor upper osoblaha basin ne sudetes slope and foreland abstract the osoblaha basin includes the north eastern slope of the zlatohorska vrchovina ridge and the north eastern foreland area of the undulating glubczyce plateau rainfall ranges from 1000 mm year in the highlands to 650 700 mm year on the glubczyce plateau the mountain part of the osoblaha basin was already penetrated by humans in prehistoric times miners extracted gold from the alluvia and later from the slope covers their activities have left traces such as extant pits in sediments iron and other ores were mined and processed there from the early middle ages onwards in the 12th or 13th century at the latest settlements and towns were founded for mining e g janov zlate hory and by farmers who tilled the land at the foot of the valley slopes this exploitation of the mountainous part of the basin caused significant clearance of beech forests as the wood was used to manufacture charcoal the deforestation of the valley slopes or the introduction of spruce forests in lieu of the beech forests changed the circulation of rain and thaw water exposed slope covers were prone to erosion or liquefaction and transfer towards the mountain valleys flood episodes caused the sedimentation of clayey overbank deposits which cover the valley floor the considerable cohesion of these sediments was conducive to the formation of meandering or anastomosing channels which were a typical feature of the osoblaha valley floor in the area around the confluence of the zlaty potok prudnik in the second half of the 18th century and in the 19th century the glubczyce plateau is a 30 40 km wide area consisting of undulating plateaux ranging from 320 to 240 m a s l these are dissected by dry valleys and descend gently towards the north fertile soils the abundance of local streams and a climate conducive to farming led to this area being settled by farming and herding communities as early as the neolithic period around 7000 bp this initiated the deforestation process and increased soil erosion shown by the colluvia accumulated in the valley heads of dry valleys and by alluvial fan sediments close to their mouths where they entered the main valleys the last stage of farming colonisation of this part of the osoblaha basin initiated by slavs had already led to the development of a dense network of settlements and considerable deforestation in the mediaeval period

increase of seawater mo inventory and ocean oxygenation during the early cambrian abstract the early cambrian radiation of macroscopic animals commonly referred as the cambrian explosion is one of the most important biological innovations in earth history because oxygen is a requirement for complex animal life it is generally accepted that ocean oxygenation may have been the environmental trigger for animal evolution but direct geochemical evidence supporting oxygen increase prior to the cambrian explosion remains sparse and insufficient to better understand the casual relationship between ocean oxygenation and animal evolution we have carried out a systematic analysis of redox sensitive trace element rste concentrations total organic carbon toc contents and pyrite morphology for the early cambrian niutitang formation of the hejiapu section northeastern guizhou province south china the new data in combination with previously published data from other sections show strong mo enrichments average of 88 ppm and high mo toc ratios average of 14 ppm wt in the euxinic black shales of the lower niutitang formation 520 ma indicating increase of the oceanic mo reservoir in the light of the positive correlation between sediment mo toc and aqueous mo in modern basins the early cambrian oceanic mo concentration is estimated as 50 nmol which is about half of the modern ocean mo concentration 105 nmol but is significantly higher than that of the mesoproterozoic oceans 10 20 nmol the marked increase in oceanic mo reservoir is therefore interpreted as recording significant rise of atmospheric oxygen and pervasive ocean oxygenation which may have facilitated the diversification of macroscopic metazoans during the early cambrian

flow of partially molten crust and the internal dynamics of a migmatite dome naxos greece 1 migmatite domes are common in metamorphic core complexes dome migmatites deform in the partially molten or magmatic state and commonly record complex form surfaces folds and fabrics while units mantling the dome display a simpler geometry typically formed by transposition during crustal extension we use field observations and magnetic fabrics in the naxos dome greece to quantify the complex flow of anatectic crust beneath an extensional detachment system the internal structure of the naxos dome is characterized by second order domes subdomes pinched synforms and curved lineation trajectories which suggest that buoyancy driven flow participated in dome evolution subdomes broadly occur within two compartments that are separated by a steep n s oriented high strain zone this pattern has been recognized in domes formed by polydiapirism and in models of isostasy dominated flow the preferred model involves a combination of buoyancy and isostasy driven processes the naxos dome may have been generated by regional n s extension that triggered convergent flow of partially molten crust at depth and the upwelling of anatectic migmatites within the dome this pattern is complicated by gravitational instabilities and or overturning of the high melt fraction crust leading to the growth of subdomes as the migmatites within the naxos dome reached a higher structural level they were affected by regional top to the nne kinematics of the detachment system dome formation therefore occurred by a combination of coeval and coupled processes upper crustal extension deep crust contraction during convergent flow of anatectic crust diapirism and or density driven crustal convection forming subdomes and north directed detachment kinematics

influence of redox conditions on animal distribution and soft bodied fossil preservation of the lower cambrian chengjiang biota abstract the exceptionally preserved chengjiang biota yunnan china is significant for understanding the rapid development of complex animal rich ecosystems during the evolutionary radiation of the cambrian however the ecological signal provided by the fossils captured in this deposit may not reflect accurately the in life community with transport and decay of carcasses being the principal processes responsible for potential modification the principal fossil bearing interval maotianshan shale member yu anshan formation is comprised of claystones of two distinct depositional origins the background beds represent slow hemipelagic deposition into deep waters while the event beds represent distal turbidites or storm generated beds each bed type has a distinct fossil assemblage and preservation mode underscoring the importance of interpreting the palaeoenvironment of each bed type here we interpret palaeo redox conditions for both the background beds and the event beds by conducting a systematic geochemical study using iron speciation 34spy 13ccarb 13ctoc and molybdenum abundance these data are from the most complete core recovered from the chengjiang fossiliferous units and allow us to distinguish redox conditions where the animals lived and where they were buried and exceptionally preserved our results demonstrate that background beds were dominated by dysoxic conditions here a diverse sponge community tolerant of low oxygen conditions lived in contrast the shallower shelf and offshore transitional environments where event beds were sourced were almost persistently oxic and it was here where the diverse chengjiang biota flourished thus the chengjiang sediments record two distinct palaeocommunities within the background and the event beds the contrasting redox conditions in close spatial proximity likely facilitated the soft bodied fossil preservation our findings provide a valuable case study in the necessity to understand ecological composition and exceptional preservation informed by environmental context

the history of holocene soil erosion in the phlious basin ne peloponnese greece based on optical dating anthropogenic induced soil erosion has occurred in the mediterranean during historic and pre historic times but precise timeframes for periods of past soil erosion are largely missing due to the lack of datable material and suitable dating methods in this study optical dating of colluvial sediments from the phlious basin ne peloponnese greece was applied the results show that soil erosion derived colluvium formed under a mediterranean type climate can be successfully dated by optical stimulated luminescence osl and a high resolution chronology of holocene soil erosion could be established colluvial formation occurred in the early holocene but increased distinctly in the seventh millennium parallel with the onset of the neolithic the start of farming activities other periods of strong colluviation are the middle and late bronze age second millennium the roman period first century to sixth century and the period since the sixteenth century rates of reduced colluviation occurred during

a geochemical framework for the application of stable sulphur isotopes to fossil pyritization pyrite formation is associated with fossils where the organic material decays by sulphate reduction or where the carbonate skeleton acts either as a nucleation substrate or induces iron sulphide precipitation by dissolution these requirements define specific combinations of porewater chemistry and saturation state with respect to carbonates and iron sulphides a review of modern marine sediments suggests that near surface porewaters are always over saturated or close to saturation with iron sulphides but are alternately rich in either dissolved iron or dissolved sulphide however significant variations in carbonate saturation state may occur with porewaters being undersaturated in the early stages of sulphate reduction but subsequently becoming oversaturated until the later stages of methanogenesis here undersaturation may return if there is a substantial input of carbon dioxide and if little alkalinity has arisen from iron reduction organic matter pyritization requires that soft tissue material decays by sulphate reduction to release dissolved sulphide with dissolved iron supplied by the surrounding porewaters the modern sediment studies therefore suggest that organic matter pyritization can occur only during the earliest stages of sulphate reduction where there are iron rich porewaters which are saturated with iron sulphides pyrite replacement of carbonate shell material requires porewater undersaturation with respect to carbonates and analogy with modern sediments suggests that these conditions occur either during the earliest stages of sulphate reduction or when methanogenesis produces undersaturation between these periods porewaters are saturated with respect to carbonates and pyrite of different morphologies can precipitate on carbonate shells sulphur isotope data provide support for these associations of porewater chemistry and style of fossil pyritization the best described examples are for soft tissue pyritization in beecher9s trilobite bed ordovician and the hunsruck slate devonian where the isotopic data are consistent with rapid early pyritization in iron rich porewaters more data are needed on shell pyritization with the range of isotopic compositions indicating formation through all stages of diagenesis