stabilization of the coupled oxygen and phosphorus cycles by the evolution of bioturbation animal burrowing and sediment mixing bioturbation began during the run up to the ediacaran cambrian boundary1 2 3 initiating a transition4 5 between the stratified precambrian6 and more well mixed phanerozoic7 sedimentary records against the backdrop of a variable8 9 global oxygen reservoir probably smaller in size than present10 11 phosphorus is the long term12 limiting nutrient for oxygen production via burial of organic carbon13 and its retention relative to carbon within organic matter in marine sediments is enhanced by bioturbation14 15 16 17 18 here we explore the biogeochemical implications of a bioturbation induced organic phosphorus sink in a simple model we show that increased bioturbation robustly triggers a net decrease in the size of the global oxygen reservoir the magnitude of which is contingent upon the prescribed difference in carbon to phosphorus ratios between bioturbated and laminated sediments bioturbation also reduces steady state marine phosphate levels but this effect is offset by the decline in iron adsorbed phosphate burial that results from a decrease in oxygen concentrations the introduction of oxygen sensitive bioturbation to dynamical model runs is sufficient to trigger a negative feedback loop the intensity of bioturbation is limited by the oxygen decrease it initially causes the onset of this feedback is consistent with redox variations observed during the early cambrian rise of bioturbation leading us to suggest that bioturbation helped to regulate early oxygen and phosphorus cycles

correlation of fluvial sequences in the mediterranean basin over the last 200 ka and their relationship to climate change macklin mark fuller i c lewin j maas g a 2002 correlation of fluvial sequences in the mediterranean basin over the last 200 ka and their relationship to climate change quaternary science reviews 21 14 15 pp 1633 1641 rae2008

andean tectonics as a cause for changing drainage patterns in miocene northern south america newdatafromneogenestratainnorthernsouthamericasuggestthatmiocenetectonisminthenortheasternandeswasresponsible for the genesis of the amazon river and changes in the drainage patterns of other major rivers such as the magdalena and the orinoco here we present a new model for the paleogeographic evolution of northern south america during the miocene in the early miocene a large part of the drainage of northwest amazonia was directed northward along the paleo orinoco river system to a deltainlakemaracaibo upliftoftheeasterncordillerainthelate middle miocene caused thefirst development of the amazon river however no connection with the atlantic was established and the amazon fed the paleo orinoco river system which drained toward the caribbean substantial andean uplift in the late miocene resultedinmajorchangesinpaleogeography theorinocochangedits course the amazon established a connection to the atlantic causing the drowning of carbonate platforms and the amazon caribbeanconnectionwasclosed thusthedrainageandpaleogeography ofnorthernsouthamericainthemiocenewerestronglycontrolled by tectonic movements in the northeastern andes

origin of phosphatic stromatolites in the upper cretaceous condensed sequence of the polish jura chain abstract the turonian stromatolite bearing condensed sequence in the polish jura chain the european epicontinental basin provides good insight into the environment of formation of cretaceous phosphatic stromatolites owing to their purely phosphatic development and negligible post depositional alteration the sequence developed as a result of slow pelagic sedimentation and microbial mat phosphatization on a submarine swell surrounded by local basins with non condensed carbonate deposition diagenesis of organic matter and dissolution of biogenic apatite were the major sources of reactive phosphorus for the microbial mat phosphatization stromatolite growth occurred due to pulses of amorphous or poorly ordered calcium phosphate precipitation followed by crystallization of carbonate fluorapatite cfa the phosphogenic environment left an imprint on the isotopic composition of limestone carbon and lattice bound carbon and sulphur in cfa and on the light rare earth element lree distribution in cfa the 13c of the stromatolite bearing sequence shows a negative excursion 1 to 3 standing in marked contrast to positive carbon values of the surrounding basinal carbonate most of the 34s values of cfa 20 to 21 fit the value range of the coeval seawater sulphate and the lree distribution shows a well defined seawater pattern this geochemical signature is indicative of intense diagenesis of organic matter at the seafloor pelagic carbonate dissolution and prolonged exposure of the deposited phosphate towards the water column the enhanced deposition and diagenesis of organic phosphorus in the stromatolitic environment reflects elevated levels of the epicontinental basin nutrification related to sea level rises and the associated oceanographic and geochemical changes

controls on phosphorus concentration and accumulation in oceanic sediments understanding phosphorus p sedimentation in the ocean is important both for quantifying outputs in the marine phosphorus cycle and for determining the controls on phosphogenesis the authigenic formation of carbonate fluorapatite and phosphorite deposition large accumulations of p rich sediments on continental margins in this study i have compiled literature data on sedimentary p concentrations and sedimentation rates from continental margins phosphogenic continental margins and open ocean environments i have also calculated p accumulation rates the product of p concentration sediment density and sedimentation rate in these settings sedimentary p concentrations exhibit a similar range in a wide variety of oceanic environments and sedimentation rate conditions for example p concentrations in continental margin sediments range from 8 to 108 mol p g 1 with sedimentation rates from 80 to 8 000 m my 1 in open ocean sediments the p concentration range is similar 7 307 mol p g 1 even though sedimentation rates are generally about 100 times lower 2 50 m my 1 the exception to this are phosphogenic environments where p concentrations are exceptionally high 580 3 700 mol p g 1 while sedimentation rates are relatively low 20 310 m my 1 phosphorus accumulation rates appear to be controlled by sedimentation rate in ocean sediments although p concentrations generally exhibit similar ranges the large difference in sedimentation rates between various environments results in p accumulation rates that are several orders of magnitude higher in continental margins 90 8 000 mol p cm 2 kyr 1 compared to open ocean sediments 2 75 mol p cm 2 kyr 1 in the case of phosphogenic environments low sedimentation rates result in p accumulation rates 80 6 300 mol p cm 2 kyr 1 that are surprisingly similar to those of non phosphogenic continental margin sediments

ediacaran δ13c chemostratigraphy of south china abstract we report new 13 c chemostratigraphic data of the ediacaran system in south china using litho and biostratigraphic markers as independent calibrators we combine new and previously published 13 c data to construct a composite 13 c profile for the ediacaran system in south china the composite curve shows in chronostratigraphic order 1 a negative 13 c excursion en1 in the doushantuo cap carbonate that overlies the ghaub age nantuo diamictite 2 a pronounced positive 13 c excursion ep1 in the lower doushantuo formation where doushantuo type acanthomorphic acritarchs red algae and animal embryos first appear 3 a mild negative 13 c excursion en2 in the middle doushantuo formation 4 a positive 13 c excursion ep2 in the upper doushantuo formation where doushantuo type acanthomorphic acritarchs micrometazoans and stem group florideophyte red algae become abundant and diverse 5 a pronounced negative 13 c excursion en3 near the uppermost doushantuo formation 6 a strongly positive 13 c excursion up to 6 3 pdb ep3 in the lower dengying formation 7 a stable 13 c plateau ca 2 5 pdb ei in the middle and upper dengying formation where abundant vendotaenid algae macroscopic ediacaran fossils biomineralized animal tubes and mostly horizontal animal traces occur and 8 a 10 negative 13 c excursion en4 immediately below the ediacaran cambrian boundary the general pattern of this composite 13 c curve is robust despite a considerable amount of variation among the 13 c profiles of different sections this composite 13 c curve provides a first order chemostratigraphic framework for the subdivision and correlation of the ediacaran system in south china

mixing of siliciclastic and carbonate sediments in shallow shelf environments the inhibiting effect that siliciclastic material has on carbonate secreting organisms has lead to the generalization that sediments composed of mixtures of carbonate and siliciclastic material should rarely form however many modern and ancient shelf deposits contain a spectrum of sediments that are of mixed composition the processes responsible for this mixing can be grouped into four categories 1 punctuated mixing where sporadic storms and other extreme periodic events transfer sediments from one depositional environment to another 2 facies mixing where sediments are mixed along the diffuse boundaries between contrasting facies 3 in situ mixing where the carbonate fraction consists of the autochthonous or parautochthonous death assemblages of calcareous organisms that accumulated on or within siliciclastic substrates and 4 source mixing where admixtures are formed by the uplift and erosion of nearby carbonate source terranes the allochemical constituents of mixed sediments are both coralgal and foram mollusc in composition the foram mollusc assemblage is the most common because of the effects of increased turbidity unstable substrates and the clogging of filter feeding mechanisms associated with a siliciclastic influx

progradational gravel beach sequences in a moderate to high energy microtidal marine environment the anatomy of progradational gravel beaches was analysed in two different tectonic settings the strongly subsiding messinian foreland basin of the eastern southern alps and the rising pleistocene marine terraces of the outer margin of the apenninic chain progradation took place near the mouths of fan delta or braid delta distributaries debouching in microtidal landlocked basins palaeo adriatic and palaeo ionian seas a wind wave climate comparable to that of the present day was characterized by periodic intense storm activity most of the beachface progradation is thought to have taken place during the post storm recovery and fair weather stages whereas the impact of storms is mostly recorded by the cutting of erosional surfaces on the beachface and by emplacement of poorly sorted and coarse grained gravels on the shoreface by storm intensified seaward trending flows and behind the highest berms by washover processes analysis of the sequences led to the identification of a number of typical divisions which are differently developed in the two settings compared here the characteristics of the apenninic sequences suggest a strongly variable wind wave climate with periodic changes from a relatively dissipative barred morphology during storms accompanied by strong longshore currents and rip development to a more reflective state typical of recovery and fair weather stages the southern alpine sequences on the other hand are characterized by poor evidence of barred morphology and of longshore currents and widespread effects of shear and gravity sorting in the lower beachface gravels these features indicate a comparatively more reflective average state due to location of beaches along the deeply embayed head of the palaeo adriatic and the very narrow directional width of the incoming wave spectrum which was almost shore normal most of the time in addition to well developed shape zonation of gravels the common presence of wave generated gravel megaripples in the southern alpine sequences indicates the greater influence of long period waves due to the greater available fetch distances in both settings the cyclicity is thought to be genetically related to minor changes of sea level

climatic and human influence on river systems and glacier fluctuations in southeast spain since the last glacial maximum abstract the semi desert environments of the mediterranean region are most sensitive to climatic changes and human land exploitation this paper is focused on the late pleistocene and holocene geomorphic evolution of southeast spain one of the driest regions in europe late pleistocene and holocene chronosequences of river terraces were established for the antas and aguas valleys respectively the deposition of up to four fluvial terraces during isotope stage 2 points to important erosion and accumulation processes at the end of late pleistocene in the vera basin in contrast to the stage 2 deposits the holocene terraces are composed of point bar deposits accumulated by meandering rivers with less sediment discharge according to the obtained 14c dating and extracted pottery fragments holocene terrace deposition occurred during the atlantic period early middle ages little ice age lia and the 20th century the most outstanding site in southern spain for studying holocene glacier shifts up to five end moraines is the veleta cirque in sierra nevada where the southernmost glacier of europe persisted during the little ice age the climate changes of the lia probably are recorded by two glacier fluctuations as indicated by 210pb dating and historical data the reconstruction of the evolution of the aguas and antas valleys stress that the aggradations of the lower terraces is mostly climate induced although during the last 500 years human interference in the landscape christian conquest mining boom of the 19th century etc may have played an important role to river dynamics

genesis of phosphorite crusts off peru abstract authigenic phosphorite crusts from the shelf off peru 9 40 s to 13 30 s consist of a facies with phosphatic coated grains covered by younger phosphatic laminite the crusts are composed of carbonate fluorapatite which probably formed via an amorphous precursor close to the sediment water interface as indicated by low f p2o5 ratios sr and ca isotopes as well as rare earth element patterns agreeing with seawater dominated fluids small negative ce anomalies and u enrichment in the laminite suggest suboxic conditions close to the sediment water interface during its formation increased contents of chalcophilic elements and abundant sulfide minerals in the facies with phosphatic coated grains as well as in the laminite denote sulfate reduction and consequently point to episodical development of anoxic conditions during phosphogenesis the peruvian phosphorites formed episodically over an extended period of time lasting from middle miocene to pleistocene individual phosphatic coated grains show a succession of phosphatic layers with varying contents of organic matter and sulfide rich phosphatic layers coated grains supposedly formed as a result of episodic suspension caused by high turbulence and shifting redox conditions episodic anoxia in the pore water induced pyritization in the outermost carbonate fluorapatite layer phosphatic coated grains were later transported to the place of crust formation where subsequent laminite formation was favored under lower energy conditions a similar succession of phosphatic layers with varying contents of organic matter and sulfide rich layers in the laminite suggests a formation mechanism analogous to that of individual coated grains

human impact in the holocene fluvial and coastal evolution of the marche region central italy abstract today the coasts of the marche region are represented by almost continuous rectilinea sand beaches except in the north at the border with the romagna region and in the central part around the conero ridge where there are active rock cliffs the sandy coasts are protected almost everywhere by artificial barriers built up as a protection against the general tendency to retreat along some tracts the coastal erosion started at the beginning of this century but became generalized after 1940 1950 this was mainly due first to the reduction in sediment supply following the improvement in agricultural techniques after the italian unification and later to the widespread extraction of gravels from the thalwegs related to the rapid increase in urban population in the 1950s however in the same period along the rivers there was a widespread creation of artificial levees to prevent lateral erosion or flooding and to extend areas suitable for agriculture following these practices the lower middle tracts of the rivers underwent a strong vertical downcutting which increased as a result of the creation of checkdams downvalley of many bridges which contributed to the store of the sediments in the upper part of the valleys at present most of the rivers have an irregular course and are deeply entrenched in the bedrock or inside their own sediments up to the beginning of the century most of the lower tracts of the valleys were characterized by strong aggradation in a braidplain system this aggradation started as early as the middle ages 1100 ad but increased after the renaissance as a consequence of a generalized deforestation of the periadriatic basin and the following severe soil erosion in the mean time the coast underwent a very fast progradation in some places more than 500 m small deltas were created at the mouths of the rivers and longshore bars and sandy beaches began to occupy the base of the active cliffs which previously extended between one river and another however in the mountain parts of the river basins a meander course existed and in many cases still exists expecially where the human interventions were of limited extent before 1000 1100 ad all the rivers had a meander pattern and at the junction with the sea entered lagoons and swamps in most cases protected by littoral barrier beaches these conditions were established earlier than the third century bc and have been attributed to the first systematic land clearance and the following soil erosion during the bronze and iron ages at that time the regional coastline became almost rectilinear but with many active cliffs between one river and another before being affected by a major human impact earlier than 4000 years bp the natural coastal environment was represented by active rock cliffs which alternated with pocket beaches corresponding to a river mouth in some rivers embayments and beaches were located up to 4 5 km inland from the present day position after the flandrian transgression the evidence presented reveals major changes that can be attributed to human impact

coated phosphate grains proxy for physical chemical and ecological changes in seawater irrespective of geologic age phanerozoic coated phosphate grains deposited beneath productive surface waters in organic rich paleoenvironments are of only two types unconformity bounded grains contain internal discordances and erosional surfaces attributable to multiple episodes of phosphogenesis and sedimentary reworking during periods of stratigraphic condensation redox aggraded grains consist of concordant concentric phosphate laminae that are intimately interlayered with circumgranular layers containing pyrite chamosite or barite recording in situ diagenetic mineralization driven by changes in pore water redox potential such changes can be attributed to variations in biological oxygen demand within suboxic pore water environments resulting from fluctuations in sedimentation rate of organic carbon redox aggraded grains are thus sensitive indicators of variations in organic carbon export and record changes in primary productivity and or ecological dynamics of the surface ocean this concept of coated grain formation necessitates a long residence time just below the sediment water interface if sedimentation rate is too high grains are rapidly buried and so removed from the zone of active phosphate precipitation coated phosphate grains can therefore be considered the granular equivalents of condensed beds these concepts are equally applicable to the interpretation of other types of coated grains and concretions that contain eh sensitive minerals such as iron bearing ooids and polymineralic concretions

neoproterozoic peritidal phosphorite from the sete lagoas formation brazil and the precambrian phosphorus cycle the neoproterozoic sete lagoas formation ca 610 ma of the sao francisco basin brazil is a succession of siltstone limestone and phosphorite phosphorite forms part of a previously unrecognized 150 to 200 m thick unconformity bounded depositional sequence lithofacies stacking patterns indicate that deposition was punctuated by higher order fluctuations in base level that produced aggradational parasequences these shallowing upward cycles record the progradation of phosphate rich intertidal flats over shallow subtidal deposits as accommodation filled the presence of mudcracks authigenic chert nodules lack of coarse terrigenous clastics and the abundance of silt with fine abraded quartz grains suggests accumulation along an arid coastline with significant aeolian input delivery of phosphorus adsorbed on aeolian fe oxyhydr oxide and clay is interpreted as having stimulated phosphogenesis in peritidal environments lithofacies associations indicate that windblown phosphorus promoted the establishment of cyanobacterial communities along the coast which produced photosynthetic oxygen and the suboxic conditions necessary for the precipitation of authigenic carbonate fluorapatite as in other precambrian phosphatic systems nearshore oxygen oases were a prerequisite for phosphorite accumulation because redox sensitive phosphogenic processes were pushed into the sediment to concentrate phosphorus in more distal anoxic environments phosphorite could not form because these biotic and abiotic processes were suspended in the water column which cycled phosphorus in sea water rather than at the sediment water interface such shallow water phosphorite is unlike larger younger neoproterozoic phanerozoic phosphatic deposits inferred to have formed in deeper upwelling related environments the increasing size of phosphatic deposits through the latest precambrian is interpreted as reflecting the progressive ventilation of the oceans during the neoproterozoic oxygenation event and resultant expansion of phosphogenic environments into distal settings the widespread cycling of bioavailable phosphorus at the sea floor not only produced the first true phosphorite giants but may have also been an important precondition for the evolution of multicellular animals

the relation between climate and river processes landforms and deposits during the quaternary abstract the extent to which river processes and morphology are dependent on climate is an old question when looking at large time scales climatic cyclicity seems to coincide with alternating events in fluvial development however the shorter the time scales at which fluvial development is considered the more it is difficult to find a close correspondence with climate evolution ultimately it appears that the response time of river processes to climatic change may restrict the sensitivity of the fluvial systems to adapt to short climatic oscillations the impact of climate on fluvial systems is largely transferred to these systems by the climate determined soil cohesion and peak discharges the latter factors are especially related to vegetation cover and permafrost conditions finally a number of basin characteristics are discussed that demonstrate that fluvial systems are not completely controlled by climate

fluvial architecture and dynamics in rising mountain chains and related basins tectonic climatic influence and human impact the flag seqs fluvial archive group subcommission for european quaternary stratigraphy siena meeting

petrology and major element geochemistry of peru margin phosphorites and associated diagenetic minerals authigenesis in modern organic rich sediments abstract new petrographic and major element geochemical data from modern peru margin upper slope outer shelf phosphorites are presented which provide insight into their origin and paragenetic relationship with other authigenic minerals glauconite pyrite and dolomite occurring in organic rich sediments glauconites are precipitated relatively early following the partial reduction of ferric iron and following this process phosphate pyrite and then dolomite precipitation take place at progressively deeper levels in the sediment in association with microbial reduction of sulfate as in many ancient economic phosphorite deposits the phosphatic facies here consist of nodules crusts coatings and strata composed of phosphatic pelletal grains ooids structureless grains intraclasts clumps and biogenic grains in association with organic rich biosiliceous sediments all are considered to have formed within a few centimeters or within a few tens of centimeters below the sediment water interface important factors that influence which morphology will tend to develop include the amount of available pore space the presence of suitable nucleation sites the amount and size of siliciclastic detritus incorporated as inclusions and the relative solution chemistries of the precipitating solutions bacterial mediation may play an important but as yet unspecified role in the precipitation process textural data and factor analysis of chemical data suggest that structureless pellets are relatively inclusion free na f mg co3 substituted pore water precipitates whereas ooids are inclusion rich pore water precipitates poor in lattice substituted components variations in nodular cement birefringence and crystallinity are suggested to have been produced by similar lattice substitutions that directly reflect pore water carbonate ion concentrations and thus relative degrees of organic matter degradation phosphate and dolomite are intimately mixed yet mineralogically distinct phases in phosphatized dolomicrites depth stratified threshold carbonate ion concentrations may control the lower limit at which phosphatic minerals may precipitate below depths of a few centimeters excessive carbonate ion concentrations and diminished reactive iron and sulfate concentrations favor the development of dolomite while precluding further development of phosphatic minerals and pyrite periodic sediment reorganization bioturbation current winnowing and erosion mass wasting etc plays an important role in both concentrating pelletal grains and maintaining nodules and crusts at critical depth levels in the sediment as well as mixing ordered mineral parageneses into complicated sequences

textural and geochemical alternations in late cenozoic bahamian dolomites dolomitized intervals of a core from san salvador island bahamas exhibit variations of two texturally and geochemically distinct end members in the pliocene section of the dolomitized interval the two end members alternate in a pattern that may reflect originally and or diagenetically modified depositional facies formerly mud free intervals locally capped by exposure surfaces are massive crystalline mimetic dolomites cm muddier sediments are replaced by friable microsucrosic dolomites ms cm and ms dolomites also differ in porosity 30 permeability 100 md mol mgco3 44 9 vs 47 7 mol oxygen isotopic composition 1 7 vs 2 7 and strontium content 241 vs 106 ppm these data indicate that depositional and diagenetic fabric are the principal controls governing the distribution of dolomite types differences in texture and geochemistry are suggested as arising through differential rates of crystallization produced as a result of variations in permeability and reactivity of the precursor sediments and rocks

variations in neoarchean microbialite morphologies clues to controls on microbialite morphologies through time the neoarchean carawine formation hamersley group western australia is a carbonate ramp that preserves diverse microbial structures which are characteristic of specific depositional environments these distinctive structures are distributed in five shallow subtidal and two deeper water facies in the oakover area of the carawine formation the shallow subtidal facies are composed of biohermal and bedded stromatolites centimetre scale ridge shaped microbialites and wavy laminated microbialites the deeper water facies are composed of fenestrate microbialites planar laminated dolostone and dolostone with rolled up microbial laminae microbialites in the carawine formation lie within a continuum of archean to proterozoic microbial facies some shallow water microbial facies in the carawine formation are similar to proterozoic facies such as large bioherms internally composed of a variety of stromatolite morphologies in contrast fenestrate microbialites grew in quiet subtidal environments and are common in archean rocks but have not been documented in similar proterozoic environments the similarity of shallow water facies across the archean proterozoic transition before and after the oxidation of the atmosphere and surface oceans indicates that stromatolite growth in shallow subtidal environments was not strongly affected by the chemical changes associated with oxidation of the oceans or by biological responses to those chemical changes rather stromatolite morphology was controlled mostly by the physical environment and the corresponding biological responses to that environment in contrast the absence of fenestrate microbialites from proterozoic deep subtidal environments suggests that the morphology of deep subtidal microbial structures was influenced by chemical or biological changes that occurred in association with oxidation of the surface oceans

precambrian phosphorites in the bijawar rocks of hirapur bassia areas sagar district madhya pradesh india the precambrian phosphorites of bijawar group of rocks show characteristics of a epicontinental sea with restricted and very shallow marine environment of formation along some shoals which existed during the iron rich precambrian times these phosphorite deposits located in the hirapur bassia areas show extensive leaching of carbonate and phosphate minerals during episodes of weathering x ray diffraction studies indicated that carbonate flourapatite is the major apatitic phase in these phosphorites while crandallite developed on the surface outcrops there is a general tendency for the depletion of co2 in these apatites leading to formation of flourapatite this co2 is an indicator of hidden weathering in the rocks major and trace element determinations of phosphorite have been used to indicate various correlation factors responsible for the concentration of elements in these precambrian leached phosphorites

microbial sequestration of phosphorus in anoxic upwelling sediments organic phosphorus is removed from the ocean by its conversion to phosphorite laboratory incubations suggest that bacteria catalyse phosphorite formation and that the rate of conversion is greatest under anoxic conditions phosphorus is an essential nutrient for life in the ocean phosphorus burial regulates marine primary production1 2 phosphorus is removed from the ocean by sedimentation of organic matter and the subsequent conversion of organic phosphorus to phosphate minerals such as apatite and ultimately phosphorite deposits3 4 bacteria are thought to mediate these processes5 but the mechanism of sequestration has remained unclear here we present results from laboratory incubations in which we labelled organic rich sediments from the benguela upwelling system namibia with a 33p radiotracer and tracked the fate of the phosphorus we show that under both anoxic and oxic conditions large sulphide oxidizing bacteria accumulate 33p in their cells and catalyse the nearly instantaneous conversion of phosphate to apatite apatite formation was greatest under anoxic conditions nutrient analyses of namibian upwelling waters and sediments suggest that the rate of phosphate to apatite conversion beneath anoxic bottom waters exceeds the rate of phosphorus release during organic matter mineralization in the upper sediment layers we suggest that bacterial apatite formation is a significant phosphorus sink under anoxic bottom water conditions expanding oxygen minimum zones are projected in simulations of future climate change6 potentially increasing sequestration of marine phosphate and restricting marine productivity

paleobathymetric influence on the development of the late ediacaran yangtze platform hubei hunan and guizhou provinces china abstract a compiled facies map based on 48 sections positioned in three chinese provinces hunan guizhou and hubei and field data emphasize the changes in depositional environments on the shelf of the ediacaran yangtze platform the facies interpretation suggests three depositional environments 1 a deep water basin with a slope facies on its margins maoping and wuhe sections hubei province 2 intertidal or shoals environments subjected to wave energy yangjiaping and zhongling sections hunan province wengan section guizhou province 3 a shallow water subtidal shelf environment subjected to currents xikou section guizhou province during the doushantuo formation time period 635 ma 551 ma condon d zhu m y bowring s yang a jin y g 2005 u pb ages from the neoproterozoic doushantuo formation china science science 308 95 98 the shelf showed an irregular bathymetry interpreted as inherited from the rifting history of the yangtze platform following the break up of rodinia approx 700 ma the tilted blocks influenced the platform development and the facies distribution locally more than the doushantuo formation time period 84 ma has been necessary to compensate the variations of bathymetry inherited of the tilted blocks geometry

large scale slope instability at the southern margin of the ediacaran yangtze platform hunan province central china thirteen stratigraphical sections from the doushantuo formation hunan province central china indicate large scale mass wasting of the yangtze platform margin between the late neoproterozoic glaciation and the earliest cambrian numerous sedimentary discontinuities due to regional slides olistostromes and slumps have modified the stratigraphy between the shallow water carbonate platform margin and the siliciclastic slope slide blocks are predominantly gently deformed and are largely composed of shallow water dolomitized limestones slide sheets may reach a regional extent of up to 5000 km 2 and are embedded in anoxic shales at an unknown water depth

primary bedded phosphorites in the campanian mishash formation negev southern israel abstract thin lentiform beds up to 1 cm thick of primary non pelletal phosphate have been found sporadically in the highly condensed anticlinal sections of the late campanian mishash formation of the central negev southern israel these primary phosphate beds are typically associated with iron rich montmorillonites of probable authigenic origin and occur at the top of upward fining phosphate dominated sequences the clay rich and primary phosphate levels are commonly truncated by amalgamated beds of high energy coarse grained phosphorites which form the basal part of these sequences with ripped up clasts of the primary phosphate commonly re incorporated in these rocks sem eds study of both the primary phosphate levels and the reworked phosphate clasts shows that they are built by a crudely stratified network of closely packed and gently compressed capsule like phosphate cells 2 5 m in external diameter and with walls of 0 5 m thick these structures are interpreted as being the synsedimentarily phosphatized remnants of former mat forming coccoid prokaryotes now represented as extracellular envelopes which intermittently colonized the mishash sea bottoms at the end of the high energy episodes differential degradation of the periphytic mat community possibly coupled with fe p redox cycling across the surficial mat iron was trapped as iron rich montmorillonites in the anoxic zone below the living mat probably resulted in an excess of dissolved phosphate immobilized as solid phases on decay resistant microbial remains which escaped total degradation development of the mat forming microbes on the mishash bottoms and their mineralization to form primary phosphorite beds occurred during periods of halted deposition which resulted in a high residence time of the mat on the seafloor and hence in intensified interface linked biogeochemical reactions ending in phosphate precipitation the restriction of primary phosphate occurrences to the condensed mishash sections of marginal palaeohigh positions strengthens previous assumptions that these zones were probably the main locus of mishash phosphate production it also points to a phosphate grain supply from marginal to basinal sites leading to the accumulation of pelletal phosphorites in the latter areas

model study of some factors influencing the resaturation of spoil following mining and reclamation abstract this study demonstrates how groundwater flow models can be used to study the long term response of groundwater flow in and around strip mines particularly once mining and reclamation are complete the two dimensional finite element model used in this study is able to simulate the actual steps in mining and reclamation and to model groundwater flow using a transient free surface approach simulations presented here are carried out on two significantly different scales in the mine scale simulations the mine occupies a major portion of the system these simulations show that spoil resaturation depends on the magnitude and distribution of recharge and the hydraulic conductivity of spoil and geological units during the early phase of spoil resaturation high gradients along the water table can develop due to first a lack of downward drainage through units below the mine or second due to spoil with a low hydraulic conductivity conversely when conditions opposite to these develop the gradients along the water table are relatively low the time over which these changes in water level occur depends upon recharge rates and the storativity of the spoil at an even smaller scale individual hills formed during reclamation are the features of interest once reclamation is complete the flow system will return to a new steady state with the position of the water table again dependent upon recharge rates and hydraulic conductivity but modified by hill size a high water table is favoured by low hydraulic conductivities high recharge rates or hills with a wide base while the addition of widely spaced surface drains is ineffective in controlling water levels discrete open drains which are closely spaced within the spoil appear much more useful generally the effect of a drain is independent of the size of the hill

paleoceanographic constraints on precambrian phosphorite accumulation baraga group michigan usa abstract the palaeoproterozoic baraga group ca 1850 1 ma of northern michigan is a 1200 m thick sedimentary succession of marine clastic iron formation chert and phosphatic sedimentary rocks that accumulated at the peak of the world s first major phosphogenic episode lithofacies stacking patterns are interpreted to record the flooding of the nuna continental margin during two sea level cycles the base of the first sequence is marked by a transgressive lag on archean basement that is transitional into a highstand accumulation of sandstones deposited in peritidal environments the bottom of the second sequence is characterized by a chert and carbonate unit with numerous subaerial exposure surfaces deposited in intertidal to supratidal environments this chert grades upward into subtidal deposits composed of interbedded organic rich mudstone and sandstone the highstand and falling stage systems tracts are composed of progradational deltaic deposits sequences were framed using the newly discovered sudbury impact ejecta horizon as a datum its emplacement approximately coincides with unrelated environmental changes that increased the delivery of river borne sediment to the nuna margin iron bearing minerals ankerite siderite and pyrite show that ferrous iron was present in peritidal to deep marine environments ankerite dominates nearshore settings where pyrite is absent pyrite occurs in deeper progradational deltaic deposits where sulfide was produced by bacterial sulfate reduction phosphorite is restricted to shallow water sediments of the first sequence and the lowstand of the second sequence precipitation is interpreted to be the result of fe redox pumping just below the sediment water interface where photosynthetically produced nearshore oxygen oases impinged on the seafloor such shallow water phosphorite accumulation is in stark contrast to many phanerozoic depositional systems in which phosphogenesis occurs across the shelf this difference likely reflects the dissimilarity in the oxygenation state of the seafloor in the precambrian fe redox pumping and thus phosphogenesis was restricted to shallow water settings with a suboxic seafloor in the phanerozoic phosphorite forms in the full spectrum of shelf environments because the entire seafloor is generally well oxygenated the concentration of bioavailable p in neritic environments during the proterozoic may have played a major role in the development of benthic microbial ecosystems and evolving eukaryotes

interpreting alluvial archives sedimentological factors in the british holocene fluvial record abstract a holocene alluvial archive of 506 dated units for great britain is analysed in terms of the sedimentation styles involved the database is classified by sedimentation unit channel sediments palaeochannel fills floodplain surface sediments floodbasins and colluvial deposits and alluvial ensemble fans and cones upland gullies and streams braided systems and active inactive meandering and anastomosing systems floodplain palaeochannel and floodbasin sediments dominate the record mostly from meandering anastomosing systems different sediment units show varied potential for recording environmental change some are relatively poorly dated with respect to the volumes of material involved whilst many dates float in periods of depositional activity which lasted for extended time periods much dated activity is autogenic and of relatively little value in interpreting external environmental influence ensembles and units are similar in age patterns in some respects commonly they exhibit sets of short term peaks in sedimentation activity but differ in others floodbasins and to an extent braided systems feature in the earlier holocene whilst dated fan deposition is more evident in the late holocene there is a general bias towards sediment units of late holocene age which probably reflects preservation factors previous british holocene alluviation models are reviewed it is suggested that the majority of earlier models reflect partial views imposed by limited regional coverage and available dating

wavy lamination in a mixed sand and gravel foreshore facies of the pleistocene hosoya sandstone aichi central japan although sandy foreshore facies are generally characterized by parallel lamination wavy lamination is predominant in the mixed sand and gravel foreshore facies of the pleistocene hosoya sandstone which crops out along the pacific coast of the atsumi peninsula aichi central japan the foreshore facies consists of three sedimentary subfacies interbeds of gravel and parallel laminated sand of the lower foreshore facies parallel laminated fine to medium sand beds containing scattered pebbles and cobbles of the middle foreshore facies and wavy laminated fine to medium sand beds containing scattered pebbles and cobbles of the upper foreshore facies a lack of erosional surfaces in the middle foreshore facies indicates the continuous accumulation of sand in flat beds under upper plane bed flow the wavy laminated sands of the upper foreshore facies exhibit erosional surfaces indicative of repeated deposition and erosion the erosional surfaces are undulatory with depressions 10 cm wide and 3 cm deep that contain scattered pebbles and cobbles these depressions reflect backwash erosion of sand around and below the pebbles and cobbles sand draping over the undulating erosional surfaces forms the wavy lamination the wavy laminated sand with scattered pebbles and cobbles is a key facies of an upper foreshore or swash zone and is a good sea level marker

early diagenetic phosphate cements in the albian condensed glauconitic limestone of the tatra mountains western carpathians early diagenetic phosphate cements are described from the albian condensed glauconitic limestone of the tatra mountains western carpathians with regard to their macro and micromorphology distribution classification and genesis the cements occur within stratigraphically condensed semi pelagic foramini feral glauconitic layers and are associated with mature hardgrounds within the tatra albian limestone phosphate cement fabrics consist of crypto to microcrystalline carbonate fluorapatite and they occur as i rim envelopes ii infillings of intraparticle porosity iii rim cement iv multiple rim cement v palisade fabric and vi cluster cement micromorphological variability of the cement fabrics results from varying texture of the cemented sediment the nature of original porosity as well as from presence of associated microbial fabrics the microbial fabrics are interpreted as fossilized coccoid cyanobacteria phosphate cementation developed under peculiar early diagenetic conditions within semi closed microenvironments rich in organic matter in the marine phreatic environment the cementation contributed to the formation of phosphatic fossils and hardgrounds the accretion of the cements was due to concentration of biologically uptaken phosphorus near the sediment water interface enrichment of pore fluids with respect to phosphate and its precipitation within restricted microenvironments phosphate cementation post dated seafloor formation of pelletal glauconite but predated partial decomposition of organic matter as well as dissolution or neomorphism of aragonite and high mg calcite phosphate cementation occurred on a carbonate platform following the submersion of urgonian reefal build ups episodes of phosphate cementation were repeated during the sedimentation of the tatra albian limestone as a response to rapid relative sea level rises and increased influence of nutrient rich tethyan waters

terminal proterozoic cyanobacterial blooms and phosphogenesis documented by the doushantuo granular phosphorites ii microbial diversity and c isotopes an unprecedented period of phosphogenesis along with massive deposition of black shales major perturbations in the global carbon cycle and the rise of atmospheric oxygen occurred in the terminal proterozoic in the aftermath of the marinoan glaciation although causal links between these processes have been postulated evidence remains challenging correlated in situ micro analyses of granular phosphorites from the ediacaran doushantuo formation in yichang south china suggested that cyanobacteria and associated extracellular polymeric substances eps might have promoted aggregated granule growth and subsequent phosphatization she et al 2013 here we present new paleontological data for the doushantuo phosphorites from yichang which combined with raman microspectroscopy and carbon isotope data further document links between the biology of cyanobacteria and phosphogenesis mapping of microfossils in thin section shows that most phosphatic granules contain microfossils that are dominated by colonies of myxococcoides along with several filamentous genera generally considered to represent cyanobacterial sheaths in addition the phosphorites and associated rocks have 13corg values in the range of 26 0 to 29 7 vpdb consistent with photoautotrophic carbon fixation with the rubisco enzyme close association of phosphorites with the marinoan tillites in stratigraphic level supports a genetic link between deglaciation and phosphogenesis at least for the doushantuo occurrence our new data suggest that major cyanobacterial blooms probably took place in the terminal proterozoic which might have resulted in rapid scavenging of bioavailable phosphorus and massive accumulations of organic matter om within a redox stratified intra shelf basin the om bound phosphorus could have liberated by microbial sulfate reduction and other anaerobic metabolisms and subsequently concentrated by fe redox pumping below the chemocline upwelling of the bottom waters or upward fluctuation of the chemocline might have brought p enriched waters to the photic zone where it was again scavenged by cyanobacteria through their eps to be subsequently precipitated as francolite the feedbacks between enhanced continental weathering cyanobacterial blooms carbon burial and accelerated phosphorus cycle thus controlled the marine biogeochemical changes which led to further oxygenation of the atmosphere and oceans ultimately paving the way for the rise of metazoans

late cenozoic flexural deformation of the middle u s atlantic passive margin despite the century long recognition of regional epeirogeny along the middle atlantic passive margin relatively few studies have focused on understanding postrift uplift mechanisms here we demonstrate that epeirogenic uplift of the central appalachian piedmont and subsidence of the salisbury embayment represent first order flexural isostatic processes driven by continental denudation and offshore deposition our results show that regional epeirogenic processes present on all atlantic type passive margins are best resolved by specific stratigraphic and geomorphic relationships rather than topography a simple one dimensional geodynamic model constrained by well dated baltimore canyon trough coastal plain and lower susquehanna river piedmont stratigraphy simulates flexural deformation of the u s atlantic margin the model represents the passive margin lithosphere as a uniformly thick elastic plate without horizontal compressive stresses that deforms flexurally under the stress of strike averaged vertically applied line loads model results illustrate a complex interaction among margin stratigraphy and geomorphology the isostatic response to denudational and depositional processes and the modulating influence of exogenic forces such as eustasy the current elevation with respect to modern sea level of fluvial terraces and correlative coastal plain deposits or unconformities is successfully predicted through the synthesis of paleotopography eustatic change and margin flexure results suggest that the middle u s atlantic margin landward of east coast magnetic anomaly is underlain by lithosphere with an average elastic thickness of 40 km flexural rigidity d 4 1023 n m the margin experiences an average long term denudation rate of approximately 10 m m y and the piedmont has been flexurally upwarped between 35 and 130 meters in the last 15 m y long term isostatic continental uplift resulting from denudation and basin subsidence resulting from sediment loading are accommodated primarily by a convex up flexural hinge physiographically represented by the fall zone our results elucidate an inherent danger in using topography alone to constrain late stage passive margin deformation mechanisms only through careful synthesis of field stratigraphic and geomorphic elements such as fluvial terraces coastal plain deposits and offshore stratigraphy can age control be extended from the offshore depositional setting to the erosionally dominated continent this study demonstrates that despite a relatively subdued topography the middle u s atlantic margin experiences progressive flexural isostatic deformation similar to that proposed for high relief margins characterized by great escarpments thus margin topographic diversity remains a function of other factors such as lithospheric composition and or structure supracrustal stratigraphy and structure degree of drainage integration drainage divide migration and climate

terminal proterozoic cyanobacterial blooms and phosphogenesis documented by the doushantuo granular phosphorites i in situ micro analysis of textures and composition abstract in order to ascertain the origin of granular phosphorites and the roles of microorganisms in phosphogenesis we conducted comprehensive petrographic surveys and correlated in situ micro analyses of granular phosphorites from the doushantuo formation near yichang south china phosphatic granules display organically zoned internal structures often associated with abundant cyanobacteria like microfossils the internal ultrastructure of the granules as documented by raman microspectroscopy scanning electron microscopy sem and transmission electron microscopy tem is characterized by randomly oriented apatite nano crystals embedded with ubiquitous carbonaceous particles in the apatite groundmass these represent primary textures formed by the rapid growth of apatite provided with abundant nucleation sites within microbial biofabrics nanosims elemental mapping revealed close correspondence of carbon and nitrogen with microfossil structures at the cellular and sub cellular level we propose that the doushantuo granules themselves were formed by microbially mediated accretionary growth followed by rapid phosphatization occurring at the sediment water interface extracellular polymeric substances eps produced by cyanobacteria would have played crucial roles in these processes by promoting aggregated granule growth in addition to providing nucleation sites for apatite crystallization while previous studies have suggested a dominant role of sulfur metabolizing microorganisms in the precipitation of phosphate in phosphorites new observations indicate that the emplacement of most sulfur bearing minerals in the doushantuo phosphorites postdate phosphatization itself our new model of phosphorite formation thus places cyanobacterial eps as an earlier key component of the mineralization of the doushantuo granular phosphorites

the phosphorus cycle phosphogenesis and marine phosphate rich deposits abstract phosphorus in the form of phosphate is an essential nutrient and energy carrier on many different levels of life and a key element in mediating between living and lifeless parts of the biosphere one of the most important aspects of the phosphorus cycle is its vital role in governing productivity thereby interacting with the exogenic part of the carbon cycle which in turn is important in regulating earth s climate phosphorus is a prime element to be traced in earth s history because it allows for the reconstruction of long term feedback mechanisms between climate environment and ecology and of global change as such marine sedimentary phosphate deposits are particularly suited to study aspects of the phosphorus cycle because in the case of ubiquity their origin may result from a general acceleration of the global phosphorus cycle sources of sedimentary phosphate are microbial breakdown of buried organic matter and redox driven phosphate desorption from iron and manganese oxyhydroxides dissolved sea water phosphate represents an additional source which may become important in the formation of phosphatic hardgrounds the main locus of phosphogenesis is near the sediment water interface but phosphogenesis also occurs at greater sediment depths current induced winnowing and transport processes along the sea floor concentrate phosphate precipitates into deposits which exhibit internal stratification patterns typical for the prevailing hydraulic energy regime in a sequence stratigraphic context phosphate deposits preferentially occur along marine or maximum flooding surfaces consequent sedimentary reworking may result in the transfer of phosphates to highstand or lowstand deposits bio chemical weathering on continents represents the most significant source of bioavailable phosphorus this implies that long term changes in marine phosphorus levels and with these changes in marine ecology productivity rates and ratios of exported carbonate carbon and organic carbon are a response to changes in continental weathering rates a compilation of marine sedimentary phosphorus burial rates for the last 160 myr suggests that natural variations have occurred that span one order of magnitude for the late jurassic cretaceous and most of the paleogene the phosphorus cycle appears to have been accelerated in times of climate warming which was most likely due to the spreading of zones of humid climate and more intense continental weathering in the neogene the phosphorus cycle appears to have responded to changes in glacially induced weathering this suggests that uniform interpretations with respect to the emplacement of major phosphorite deposits should be treated with caution integrated analyses of the sedimentary and biogeochemical context of phosphorite occurrences may help to identify paleoenvironmental conditions as well as to improve our understanding of periods of enhanced phosphate accumulation periods which were usually characterized by steep gradients in the development of climate and environment with regard to the complexity of feedback mechanisms between the phosphorus cycle and the biosphere the present day input rates of phosphate into the world s oceans should be of great concern they are more than doubled by anthropogenic means and affect ecological systems on a rapidly increasing scale

sedimentary phosphate and associated fossil bacteria in a paleoproterozoic tidal flat in the 1 85 ga michigamme formation michigan usa abstract phosphorus is a nutrient fundamental to life and when it precipitates in modern environments bacteria are intimately involved in its release concentration and mineralization preserved fossil bacteria in phosphate crusts and grains from the ca 1850 million year old bijiki iron formation member of the michigamme formation michigan provide insight into the longevity and nature of this relationship the michigamme formation accumulated near the end of the earth s initial phosphogenic episode ca 2 2 and 1 8 ga to produce one of the first granular phosphorites phosphatic lithofacies consist of fine to medium sand sized francolite peloids concentrated on bedding surfaces in peritidal facies granular beds are up to 2 cm thick and peloids are often partially to completely replaced by dolomite and chert the grains contain organic matter and pyrite framboids that suggest bacterial breakdown of organic matter and bacterial sulfate reduction the peritidal nature of phosphorite in the michigamme formation is in sharp contrast to phanerozoic phosphogenic environments in deeper coastal upwelling settings peritidal settings were well suited for phosphogenesis under the very low oxygen and low dissolved sulfate levels of the paleoproterozoic as cyanobacteria produced oxygen in shallow water and evaporation led to increased sulfate concentrations such concomitant processes helped establish focused redox interfaces in the sediment that chemosynthetic bacterial communities sulfur oxidizers reducers forms that concentrate p and possibly iron oxidizers could exploit phosphate released from organic matter by heterotrophic bacteria and fe redox pumping was further concentrated by these chemotrophs a process that forms late neoproterozoic to phanerozoic phosphorites but on a much larger scale this early example of a granular phosphorite demonstrates that like their phanerozoic counterparts paleoproterozoic phosphorites are the concentrated indirectly biomineralized products of bacterial communities but unlike younger analogs which accumulated across subtidal shelves and shelf margins these ancient deposits formed only in tidal flat settings where phosphogenic redox processes could be established in the sediment from this early beginning the zone of phosphogenesis likely migrated into deeper water settings as oxygen and sulfate levels rose expanding the zone of chemosynthetic bacterial and associated phosphogenesis across the shelf

holocene sea level history evidence from coastal sediments of the northern rio grande do norte coast ne brazil the holocene sea level history of the mesotidal northern rio grande do norte coast ne brazil was reconstructed from sedimentology and ams radiocarbon dating of beachrock and tidal lagoonal sediments at 7000 cal year bp at 3 m sea level stood and passed the modem sea level 6700 cal year ago the holocene highstand reached 1 3 m above modem sea level at 5900 cal year bp as determined by beachrock samples from the uppermost part of an intertidal foreshore deposit a 5700 cal year old shell midden overlies this beachrock that represents the spring tide sea level after the highstand sea level dropped to its present position beachrock samples from intertidal upper foreshore deposits were used for elevation and age control beachrock positions with their error bars are all within the tidal range envelope therefore no secondary oscillations during the sea level fall can be confirmed a linear sea level fall of this magnitude can be explained by the mechanism of equatorial ocean syphoning c 2005 elsevier b v all rights reserved

integrated ediacaran sinian chronostratigraphy of south china abstract the ediacaran period was a critical time in the history of life and earth understanding the complex interactions between geological and biological events during this interval requires high resolution chronostratigraphy thanks to its uniquely favorable palaeogeographic setting south china is an ideal region for constructing a framework for global chronostratigraphic correlation of ediacaran strata here continuous ediacaran successions contain both siliciclastic and carbonate rocks that range from shallow to deep marine and contain rich fossil assemblages showing a variety of preservation styles as part of the present study 62 reference sections distributed throughout the yangtze platform were investigated analyses of the sedimentary facies and sequence stratigraphy of more than 40 sections revealed four major sequences in the shallow marine facies three major sequence boundaries occur respectively in the middle and upper parts of the doushantuo formation and in the middle part of the dengying formation subdivision and correlation of the ediacaran successions of the yangtze platform based on sequence stratigraphy is congruent with the carbon isotope chemostratigraphy of 12 reference sections 1075 samples the sequence boundary sb2 in the middle part of the doushantuo formation is suggested here as the lower xiadongian upper yangtzean series boundary of the ediacaran which coincides with several globally recognizable events namely 1 the end of the neoproterozoic glaciations 2 the first appearance of animals 3 the sudden increase in the diversity of acanthomorphic acritarchs and 4 a negative 13 c excursion the ediacaran system of south china may be subdivided into five stages furthermore the criteria for defining these stages may be applicable throughout the world also the composite carbon isotope profile of the ediacaran of south china can be used as a global reference for chronostratigraphic subdivision and correlation in addition to the globally recognizable negative 13 c excursion in the cap carbonate at the base of the ediacaran the negative 13 c excursion in the uppermost doushantuo wonoka shuram interval represents another globally correlatable major excursion the positive 13 c excursion immediately following the uppermost doushantuo excursion and ending at 548 ma is also useful for global correlation current ediacaran chronostratigraphy and global correlations indicate that the upper doushantuo wonoka shuram negative 13 c excursion ranges from ca 560 ma to 551 ma and therefore coincides with the evolutionary renovation of life feedback between evolutionary innovation and geochemical cycling was the key mechanism for this unique and most strongly negative 13 c excursion in earth history our chronostratigraphic correlations also imply that the earliest known metazoan biotas namely the weng an and characteristic ediacaran biotas do not constitute two temporally separate evolutionary lineages as proposed previously but represent two parallel evolutionary pathways preceding the cambrian explosion of animal life

oxygenation of the earth s atmosphere ocean system a review of physical and chemical sedimentologic responses abstract the great oxidation event goe is one of the most significant changes in seawater and atmospheric chemistry in earth history this rise in oxygen occurred between ca 2 4 and 2 3 ga and set the stage for oxidative chemical weathering wholesale changes in ocean chemistry and the evolution of multicelluar life most of what is known about this important event and the subsequent oxygenation history of the precambrian earth is based on either geochemistry or data mining published literature to understand the temporal abundance of bioelemental sediments bioelemental sediments include iron formation chert and phosphorite which are precipitates of the nutrient elements fe si and p respectively because biological processes leading to their accumulation often produce organic rich sediment black shale can also be included in the bioelemental spectrum thus chemistry of bioelemental sediments potentially holds clues to the oxygenation of the earth because they are not simply recorders of geologic processes but intimately involved in earth system evolution chemical proxies such as redox sensitive trace elements cu cr v cd mo u y zn and ree s and the ratio of stable isotopes 56fe 53cr 97 95mo 98 95mo 34s 33s in bioelemental sediments are now routinely used to infer the oxygenation history of paleo seawater the most robust of these is the mass independent fractionation of sulfur isotopes mif which is thought to have persisted under essentially anoxic conditions until the onset of the goe at ca 2 4 ga since most of these proxies are derived from authigenic minerals reflecting pore water composition extrapolating the chemistry of seawater from synsedimentary precipitates must be done cautiously paleoenvironmental context is critical to understanding whether geochemical trends during earth s oxygenation represent truly global or merely local environmental conditions to make this determination it is important to appreciate chemical data are primarily from authigenic minerals that are diagenetically altered and often metamorphosed because relatively few studies consider alteration in detail our ability to measure geochemical anomalies through the goe now surpasses our capacity to adequately understand them in this review we highlight the need for careful consideration of the role sedimentology stratigraphy alteration and basin geology play in controlling the geochemistry of bioelemental sediments such an approach will fine tune what is known about the goe because it permits the systematic evaluation of basin type and oceanography on geochemistry this technique also provides information on how basin hydrology and post depositional fluid movement alters bioelemental sediments thus a primary aim of any investigation focused on prominent intervals of earth history should be the integration of geochemistry with sedimentology and basin evolution to provide a more robust explanation of geochemical proxies and ocean atmosphere evolution

palaeokarst evidence for widespread regression and subaerial exposure in the middle katian upper ordovician of baltoscandia significance for global climate we report on widespread and contemporary palaeokarst in the middle katian upper ordovician of sweden estonia and latvia the first major palaeokarst horizon to be reported from the ordovician of baltoscandia the solution features occurwithin a fewmetres of thick zone of limestone immediately belowthe widespread fjacka shale and are related to an unconformity with preserved palaeorelief in the slandrom limestone in sweden and the time equivalent saunja formation in estonia and latvia facies evidence for a karst origin comes fromseveral outcrops and core sections and includes 1 frequent karren likemorphologies interpreted as swiss cheese karst sensu baceta et al 2001 2 local occurrences of solution collapse breccia 3 presence of bladed pseudospar crystals in solution cavities and 4 carbon isotope values indicating meteoric influence to the succession these findings are herein put in context with previously reported large scale erosional channels that may cut down several tens of metres below the fjacka shale in the subsurface baltic sea area and with regional anomalous thickness variations in the slandrom limestone and saunja formation all together forming strong support for regional exposure of the baltoscandian continent in the middle katian high resolution stable isotopic data show that the regression and lowstand of sea level overlap with thewaynesville carbon isotope excursion it resulted in basin wide cessation of carbonate production near the amorphognathus superbus and a ordovicicus conodont zonal boundary the contemporary development of palaeokarst in different confacies belts of the basin suggests that this was an extraordinary sea level lowstand herein interpreted as reflecting a middle katian glaciation less

phosphorus phosphorites and skeletal evolution at the precambrian cambrian boundary clustering of sedimentary phosphate deposits around the precambrian cambrian boundary is related to a global phosphogenic event this event probably resulted from a complex interplay of factors and had a profound effect on the biota with high concentrations of phosphorus in the photic zone producing an increase in the total shallow marine biomass faunal diversification the precipitation of skeletal structures and explosive evolution

past hydrological events reflected in the holocene fluvial record of europe abstract a comprehensive database of radiocarbon dated fluvial units in great britain poland and spain has been compiled to investigate the relationship between environmental change flooding and holocene river dynamics following the methodology recently developed by macklin and lewin macklin m g lewin j 2003 river sediments great floods and centennial scale holocene climate change journal of quaternary science 18 101 105 radiocarbon dates in fluvial sequences that coincide with a modification in sedimentation rate or style have been highlighted allowing geomorphologically significant changes in holocene river activity to be identified data analysis has been undertaken at both national and sub national scales and on catchments of different size type and land use history multiple phases of higher flood frequency characterized by accelerated erosion and sediment deposition on floodplains are recognized and compared with a range of climate proxies the relative and varying roles of climate and land use on river dynamics are considered and the value of the database for reconstructing past hydrological events as well as for predicting river response to future environmental change is assessed

long term fluvial archives in nw france response of the seine and somme rivers to tectonic movements climatic variations and sea level changes the seine and the somme are the two main rivers flowing from northwestern france into the channel during the pleistocene cold stages both rivers were tributaries of the river manche which was exporting sediments into the central deeps of the channel the river seine has a very well developed terrace system recording incision that began at around 1 ma the same age is proposed for the beginning of the main incision in the somme valley on the basis of morphostratigraphy pedostratigraphy palaeontology palaeomagnetism and esr datings the uplift rate deduced from analysis of the seine and somme terrace systems is of 55 to 60 m ma since the end of the lower pleistocene the response of the two rivers to climatic variations uplift and sea level changes is complex and variable in the different parts of the river courses for example the evolution of the lower seine system is influenced by uplift and climate changes but dominated by sea level changes in the middle seine the system is beyond the impact of sea level variations and shows a very detailed response to climatic variations during the middle and upper pleistocene in a context of uplift the somme valley response appears to be more homogeneous especially in the middle valley where the terrace system shows a regular pattern in which incision occurs at the beginning of each glacial period against a general background of uplift nevertheless the lower somme valley and the palaeo somme in the channel area indicate some strong differences compared with the middle valley influence of sea level variations and probably differences in rates of tectonic uplift between the channel and the present continent the differences in the responses of the two river valleys during the pleistocene are related to differences in the size of the fluvial basins to the local tectonic characteristics to the geometry of the platform connected to the lower parts of the valleys and to the hydrodynamic characteristics of each river finally it is shown from these examples that the multidisciplinary study of pleistocene rivers is a very efficient tool for the investigation of neotectonic activity

the ree composition and petrography of apatite in 2ga zaonega formation russia the environmental setting for phosphogenesis the first significant p rich deposits appear in the global rock record during the paleoproterozoic around 2 ga however the specific triggers that led to apatite precipitation are still under debate the ca 2 ga zaonega formation karelia russia contains p rich intervals in its upper part with abundantly occurring apatite these apatites have been studied for their rare earth element ree composition using laser ablation inductively coupled plasma mass spectrometry la icp ms with an emphasis on the environmental condition during phosphogenesis petrographic observations by scanning electron microscopy sem integrated with la icp ms results allow recognition of variously recrystallized apatite and distinction of best preserved diagenetic apatite which presumably records syn depositional ree characteristics diagenetic apatite exhibits moderately negative ce anomalies that indicate an at least partially oxygenated water column a variable but typically positive eu anomaly is consistent with geologic evidence suggesting intensive magmatic activity and hydrothermal influence during apatite precipitation we conclude that phosphatic sediments in the paleoproterozoic zaonega formation record phosphogenesis in a vent seep influenced setting that experienced fluctuating redox conditions at the sediment water interface

phosphorus accumulation in marine sediments and the oceanic phosphorus cycle ideas about key factors in the oceanic mass balance of dissolved reactive phosphate have changed substantially i present an integrated overview of these here with an emphasis on evaluating the burial sinks for p and defining areas needing further research the major source of reactive p to the ocean is river input reactive p is delivered to the oceanic sediment water interface primarily in particulate organic matter p scavenged by hydrothermal iron rich oxyhydroxide particles with uptake in proportion to deep water phosphate concentrations represents a substantially smaller flux to the sediment water interface diagenetic transformations are important influences on the form of reactive p burial in marine sediments p burial occurs with organic carbon burial and as p associated with iron rich oxyhydroxide particles and coatings formation of authigenic p rich phases presumably apatite at the expense of organic p and oxide associated p is significant in open ocean marine sediments the authigenic p sink may represent a substantially larger portion of the sedimentary burial than indicated by previous estimates focused on p burial in organic rich continental margin sediments

economic phosphorite from the ediacaran doushantuo formation south china and the neoproterozoic cambrian phosphogenic event abstract phosphorite of the ediacaran doushantuo formation accumulated in the central guizhou province during the neoproterozoic cambrian phosphogenic event producing the first true phosphorite giant in earth history deposition is interpreted to have occurred on a wave dominated epeiric platform along the northern margin of the qianzhong uplift lithofacies stacking patterns and two paleokarst surfaces record phosphogenesis through at least two sea level cycles as in younger phanerozoic epeiric sea phosphorites the delivery of upwelled phosphorus is interpreted to have stimulated phosphogenesis in a range of shallow water environments ten phosphatic and associated lithofacies are recognized in the doushantuo formation wavy and horizontal laminated pristine facies were the locus of phosphogenesis and reflect the authigenic precipitation of francolite in accumulating fine sediment granular cross stratified phosphorite is interpreted to have been produced through storm wave winnowing of pristine facies and the subsequent transport redeposition and concentration of phosphatic peloids into economic beds beds with the highest concentration of phosphorus formed in shallow wave agitated environments around paleo topographic highs paragenetic analysis suggests that secondary meteoric processes further enriched the phosphorus content 35 wt of these granular beds during sea level lowstands such aerially extensive upwelling related phosphorite contrasts paleoproterozoic and neoproterozoic phosphatic deposits throughout much the proterozoic francolite precipitation was restricted to shallow water photosynthetic oxygen oases where redox sensitive phosphogenic processes were focused in the sediment the doushantuo formation is interpreted to record the oxygenation of the water column and concomitant expansion of phosphogenic environments during the neoproterozoic oxygenation event this progressive ventilation of the deep ocean forever changed the biogeochemical cycling of phosphorus in the marine realm and set the stage for the deposition of phosphorite giants that punctuate the phanerozoic stratigraphic record

reappraisal of the ages of neoproterozoic strata in south china no connection with the grenvillian orogeny the jiangnan fold belt separates the yangtze and cathaysia blocks in south china and has long been considered grenvillian in age in order to place south china in central rodinia it consists of deformed early neoproterozoic strata that are unconformably overlain by undeformed late neoproterozoic strata and intruded by undeformed and unmetamorphosed granitic plutons zircons from the early neoproterozoic strata yield u pb ages as young as 830 ma and one granitic pluton has a zircon u pb age of ca 827 ma the 830 ma mafic rocks along the southeastern margin of the yangtze block have arc affinity geochemical characters whereas mafic rocks younger than 830 ma have typical ocean island basalt oib like compositions thus we suggest that the early neoproterozoic strata were deposited on an active continental margin prior to amalgamation of the yangtze and cathaysia blocks at ca 830 ma the overlying late neoproterozoic strata were deposited in the intracontinental rifted nanhua basin at 820 730 ma and probably reflect backarc spreading above the long lived 950 735 ma oceanic subduction zone along the northern and western margin of the yangtze block this model is consistent with the secular tectonic evolution of south china during the neoproterozoic the jiangnan fold belt is therefore not a grenvillian feature as previously suggested and there is no evidence to place south china in central rodinia instead we believe that south china was located in a marginal position relative to this supercontinent

pb pb ages of neoproterozoic doushantuo phosphorites in south china constraints on early metazoan evolution and glaciation events the pb pb isochron ages of 576 14 ma for the upper part of the upper phosphorite bed upb this study and 599 4 ma for the lower part of the upb earth planet sci lett 201 2002 203 in the doushantuo formation in the weng an area south china suggest that the deposition of the upb lasted at least 5 ma and indicate that the observed microfossil assemblage animal remains multicellular algae and giant process bearing acritarchs in the doushantuo formation predates all well dated diverse ediacaran assemblages and represents the earlier paleontological record of eukaryotes radiation on earth the 576 14 ma age in the upper part of the upb approximates the age of a negative delta 13 c excursion near the boundary between the doushantuo and the overlying dengying formation if the doushantuo dengying boundary at the weng an area is equivalent to that in the yangtze gorges area this negative excursion might correlate to a post marinoan glaciation in south china suggesting that the ice age following doushantuo sediment deposition is younger than 590 ma the 599 4 ma age in the lower part of the upb earth planet sci lett 201 2002 203 represents the minimum age of the nantuo diamictites which are generally correlated with the marinoan glaciation c 2004 elsevier b v all rights reserved

co evolution of eukaryotes and ocean oxygenation in the neoproterozoic era the oxygenation of the earth s deep oceans is often thought to have triggered the evolution of simple animals a review article proposes that instead the evolution of animal life set off a series of biogeochemical feedbacks that promoted the oxygenation of the deep sea

simulation of changes in ground water levels associated with strip mining coal strip mining can influence ground water levels both spatially and in time in the vicinity of a mine the magnitude extent and timing of such changes are not however well known through the use of a finite element model that was developed specifically to study these problems it is possible to solve for the hydraulic head distribution within a two dimensional region and for the position of the water table and seepage faces in a mined area as a function of time sensitivity analyses conducted with the model show that strip mining not only influences water levels during the mining and early post mining period but also show that the most significant effects are observed during the re establishment of a steady state flow system following mining the magnitude and extent of changes in ground water levels are controlled by at least four important hydrogeological parameters 1 the presence of local discharge areas or sources of recharge 2 the character of the post mining landscape 3 changes in the rate of recharge through the spoil and 4 changes in the hydraulic conductivity of the spoil relative to the undisturbed geologic materials the timing of water level changes depends upon features of the flow system such as how efficiently water is able to move to the low in hydraulic potential caused by mining and also upon the storativity of the mine spoil all of the simulations indicate that long times are required for the flow system to re establish steady state conditions following mining such results imply that the maximum impact of mining at some sites may not be felt until many years following the cessation of mining

carbon isotope chemostratigraphy and sedimentary facies evolution of the ediacaran doushantuo formation in western hubei south china abstract the doushantuo formation of south china consisting of intercalated siliciclastic and carbonate rocks which exhibit considerable variation in thickness and sedimentary facies is one of the key sedimentary units in the world for understanding ediacaran geobiological processes however stratigraphic correlation and sedimentary facies evolution of the doushantuo formation remain controversial sedimentary facies analysis of the well known sections of the yangtze gorges area and new sections in northern yichang western hubei indicate that the doushantuo succession in the yangtze gorges area was deposited in an offshore intra shelf basin within the yangtze platform in contrast the doushantuo formation in the northern yichang area which is characterized by one or a few phosphate rich horizons represents deposition on the subtidal or intertidal shelf and so is similar to the succession in the weng an area central guizhou province the carbon isotope profiles of the different sections exhibit significant variation which is interpreted to result from facies differences sequence and high resolution carbon isotope stratigraphy have clarified problematic correlations and the temporal relationship between fossil assemblages of the doushantuo formation on the yangtze platform the results confirm that a prominent negative 13ccarb excursion baince nadir down to 5 in the middle portion of the second sequence of the doushantuo formation is a widely traceable event baince together with three other 13ccarb excursions namely cance at the base wance near the first sequence boundary near the middle and dounce at the top of the doushantuo formation constitute a complete carbon isotope profile for the doushantuo formation that reflects contemporaneous seawater and so serves as a reference chemostratigraphic profile for global stratigraphic correlation and for evaluating the chemical evolution of seawater during the ediacaran period

simulation of groundwater mounding at a west australian mine site few studies exist that investigate the potential impact of groundwater mounding due to mining near an environmentally sensitive area in a real world scenario this paper presents a case study in which the development and extent of groundwater mounding due to mining near the shark bay world heritage property sbwhp in western australia wa has been simulated a numerical model was developed that enabled a detailed simulation of groundwater level response to the discharge of a water saturated sand slurry during mining at the project site near coburn in wa the simulations showed that after a mining period of around two and a half years a groundwater mound of around 2 5 m would develop along the margins of the open pit at the sbwhp boundary 500 m further into the sbwhp the groundwater mound is predicted to be around 1 m high a depth to water analysis showed that the groundwater may come within 4 m of the surface in the area of a sand dune swale that traverses from sw to ne near the sbwhp boundary the results of these analyses provide a perspective of mine related impacts in a unique environment the results have been included in an environmental impact assessment eia and used for mine water balance predictions

source rock potential of the phosphorite bituminous chalk marl sequence in jordan abstract the phosphorite and the overlying oil shale succession in central and eastern jordan has been studied for its organic matter composition maturation hydrocarbon potential and sedimentological implications pristine phosphorite was authigenically precipitated from interstitial solutions in ventilated environments later they were reworked and winnowed to produced the granular phosphorites possibly as wave or storm sand bodies the oil shale was deposited in the same basins where restricted water circulation and subsequent hypersalinity led to more reducing conditions and better organic matter preservation both facies represent a high bio productivity regime associated with paleo upwelling on the shallow southern epicontinental shelf of the tethys ocean the organic matter is dominantly amorphous and the extractable part is high kerogen is type ii s to type iii all maturity parameters investigated proved it to be immature e g r0