rare earth elements in the sediments of the north atlantic ocean amazon delta and east china sea reinterpretation of terrigenous input patterns to the oceans

the distribution of rare earth and minor elements in manganese nodules and sediments from the equatorial and s w pacific abstract 62 manganese nodules and 17 associated sediments from the equatorial and s w pacific have been analyzed for a number of elements including the rare earth elements ree by instrumental neutron activation sc co as hf th and ree occur in higher concentrations in s w pacific than in equatorial pacific nodules reflecting the higher iron content of the s w pacific nodules these elements are probably incorporated nondiscriminantly into the iron oxyhydroxide structure by direct sorption from seawater because they are too large to be incorporated into the manganese oxide structure the highest ce la ratios are also found in the s w pacific nodules this may result from the fact that these nodules lie beneath the path of the fast flowing well oxygenated antarctic bottom water aabw which facilitates oxidation of ce to the tetravalent state if so this supports the idea that the ce la ratio of manganese nodules is an important redox indicator negative cerium anomalies were noted for nodules from areas f and g can be interpreted on the same model the ree contents in equatorial pacific siliceous oozes and s w pacific red clays are similar on a carbonate free basis the ce la ratio of the s w pacific red clays is however much higher than that of the equatorial pacific sediments possibly reflecting the preferential oxidation of ce to the tetravalent state beneath the aabw there appears to be no systematic relationship between the ree abundance in the nodules and their associated sediments although absolute ree abundances are higher in nodules than in their associated sediments nodules with the highest ce la ratios are however found on sediments with the highest ce la ratios the principal difference in the ree distribution pattern of the nodules and sediments lies in the well known cerium anomaly which is positive to slightly negative for nodules and always negative for sediments

metal accumulation rates in northwest atlantic pelagic sediments measurements of 230th 87sr86sr and twenty four metals were made on cores from the nares abyssal plain the sediment is characterized by slowly accumulating 0 3 0 7 g cm2 103 yr pelagic red clays and rapidly deposited grey clays transported by turbidity currents despite their colour differences and the enrichment of mn fe cu co ni zn v and to a lesser degree the rare earths in the red clays sr isotope evidence demonstrates that the clays have the same terrigenous origin the excesses of metals in the red clays have been attributed to metal removal from the water column and a comparison with the grey clays has enabled the authigenic fluxes of metals to be estimated the fluxes obtained are in the ranges 20 50 mol cm2 103 yr for mn and fe 0 1 0 4 mol cm2 103 yr for cu co ni zn v sr and ce 10 20 nmol cm2 103 yr for la and nd and 0 5 3 nmol cm2 103 yr for sm eu gd dy er and yb authigenic fluxes of y nb cr zr rb u and th were not resolvable fluxes appear to be near constant on the plain but comparison with other areas shows that they are quite variable both between and within ocean basins the chief factor controlling authigenic fluxes is the geochemical abundances of the elements but fractionation within both the transition element and rare earth series can be recognized from inter element comparisons and from differences in fluxes between atlantic and pacific red clays corresponding to the oceanic reactivities of the elements

variable eocene miocene sedimentation processes and bottom water redox conditions in the central arctic ocean iodp expedition 302 abstract in 2004 integrated ocean drilling program expedition 302 arctic coring expedition acex to the lomonosov ridge drilled the first central arctic ocean sediment record reaching the uppermost cretaceous 430 m composite depth while the neogene part of the record is characterized by grayish yellowish siliciclastic material the paleogene part is dominated by biosiliceous black shale type sediments the lithological transition between paleogene and neogene deposits was initially interpreted as a single sedimentological unconformity hiatus of 26 ma duration separating eocene from miocene strata more recently however continuous sedimentation on lomonosov ridge throughout the cenozoic was proclaimed questioning the existence of a hiatus in this context we studied the elemental and mineralogical sediment composition around the paleogene neogene transition at high resolution to reconstruct variations in the depositional regime e g wave current activity detrital provenance and bottom water redox conditions already below the hiatus mineralogical and geochemical proxies imply drastic changes in sediment provenance and or weathering intensity in the hinterland and point to the existence of another earlier gap in the sediment record the sediments directly overlying the hiatus the zebra interval are characterized by pronounced and abrupt compositional changes that suggest repeated erosion and re deposition of material regarding redox conditions euxinic bottom waters prevailed at the eocene lomonosov ridge and became even more severe directly before the hiatus with detrital sedimentation rates decreasing authigenic trace metals were highly enriched in the sediment this continuous authigenic trace metal enrichment under persistent euxinia implies that the arctic trace metal pool was renewed continuously by water mass exchange with the world ocean so the eocene arctic ocean was not fully restricted above the hiatus extreme positive ce anomalies are clear signs of a periodically well oxygenated water column but redox conditions were highly variable during deposition of the zebra interval significant mn enrichments only occur above the zebra interval documenting the miocene establishment of stable oxic conditions in the arctic ocean in summary extreme and abrupt changes in geochemistry and mineralogy across the studied sediment section do not suggest continuous sedimentation at the lomonosov ridge around the eocene miocene transition but imply repeated periods of very low sedimentation rates and or erosion

application of the ce anomaly as a paleoredox indicator the ground rules much attention has been paid in recent years to the potential application of the ce anomaly measured in various marine phases as a paleoceanographic indicator of widespread marine anoxia in this paper we present and discuss results from recent studies of present day rare earth element ree distributions and hence ce anomaly distributions in the marine environment which are particularly pertinent to paleoceanography subsequently we review and discuss the validity of the recent literature in which ce anomalies have been employed as paleoredox indicators

the assessment of ree patterns and 143nd 144nd ratios in fish remains abstract the ree content and isotopic composition of sr and nd have been determined in fish teeth ranging in age from the trias to the present and from various localities mostly around the atlantic these measurements have been carried out on selachian and teleost remains from the same locality in togo and show no appreciable difference which suggests with the help of a mass balance calculation of the ce anomaly that diagenetic effects are not responsible for the ree enrichment of biogenic phosphates one group of fossil teeth has about 3 times the ree abundances of shale and a shale normalized pattern with a minimum at sm it is thought to reflect deposition in the open sea environment a second group has ree concentration about 10 times higher than the first group with either a regular light ree enrichment or more frequently a maximum in the middle ree both being probably indicative of deposition in estuarine or near shore conditions the shape of the ree spectra and the size of the ce anomaly can be used semi quantitatively to determine the depth of deposition the results presented here on late cretaceous eocene fish teeth samples from morocco reflect an increasing influx of deep waters with a lowla yb ratio and strong negative ce anomaly which agrees well with the evolution of sediment chemistry and microfauna associations in contrast nd is typical of the water mass in which the fish debris decayed examples of nearly isolated basins identified with nd isotopes include the south atlantic prior to the lutetian nd 13 5 the miocene persian gulf nd 3 1 and bolivia during the late cretaceous nd 12 8 togo and guinea bissau results suggest that in the south atlantic the meridional oceanic circulation had not started before 45 ma ago combination of ree and nd data suggests that the assignment of jurassic cretaceous samples measured so far to open sea water masses is still ambiguous

cycling of dissolved rare earth elements in chesapeake bay the measurement of dissolved rare earth elements ree in the surface waters water column of anoxic basins and pore waters in chesapeake bay has provided new insights to the biogeochemistry and estuarine chemistry of ree all dissolved ree from the riverine source show large scale removal in the lower salinity zone 0 10 the shale normalized pattern of dissolved susquehanna river water is opposite in form to that of surface sediments in the bay the former is enriched in heavy ree hree while the latter are enriched in light ree lree neither component has a flat pattern normally assumed for river transported ree to the ocean the dissolved lree i e la ce nd sm and eu are enriched 3 to 9 times in the oxygen depleted deep waters over their concentrations in the oxic surface waters in contrast hree er yb and lu are slightly depleted all ree concentrations in the two surface 0 2 cm pore waters are greatly enriched 8 17 times 43 times for ce relative to oxygen depleted bottom waters and have relative abundances opposite to those of their sediments while ce has a positive anomaly in the pore waters negative anomalies exist in the oxygen depleted bottom waters the ree are participating in a set of complex biogeochemical cycles within the water column and surface sediments fractionation of ree during these cycles leads to the preferential enrichment of lree in the seasonally oxygen depleted bottom waters it is proposed that this fractionation is coupled to redox cycles of mn and fe and the interaction of dissolved ree with suspended particles and surficial sediments

rare earth element fluxes and geochemical budget in the eastern equatorial pacific rare earth element ree patterns and flux measurements of sediment traps sediments and nodules from the eastern tropical pacific demonstrate the dominance of ree supply to the sea floor by particle settling quantitative partitioning of the particle flux reveals that biogenic debris is the major ree carrier in shallow depths however the labile particles are surpassed in importance by alumino silicate particles at greater depths regeneration of biogenic associated ree appears responsible for la ce variations in the particle flux with depth and provides the primary source of ree accreted by nodules

rare earth element deposition in pelagic sediment at the cenomanian turonian boundary exmouth plateau odp site 762 eastern indian ocean includes a section of sediment that spans the cenomanian turonian boundary ctb and was deposited along a continental margin during a period of widespread oceanic 09 deficiency the rare earth element ree content of pre and post boundary sediment is similar to that of present day continental slope material deposited in well oxygenated seawater whereas the ctb section is characterized by significantly depleted ree abundances a bulk ce anomaly that increases to maximum of 1 0 and a ree pattern that resembles that of present day fluvial material we suggest the change in ree patterns reflects release of scavenged rees upon reductive dissolution of authigenic fe mn oxyhydroxides such that sediment deposited during the ctb is dominated by the lithogenous ree fraction these results are consistent with recent models concerning pervasive fractionation of mn and fe and redirection of mn in pelagic ctb waters

identification of the guadalupian lopingian boundary in the permian in a bedded chert sequence south china abstract middle upper permian conodont biostratigraphy was examined in a bedded chert section in dachongling area of southeastern guangxi zhuang autonomous region south china four conodont zones were recognized namely jinogondolella granti zone clarkina postbitteri hongshuiensis zone clarkina postbitteri postbitteri zone and clarkina dukouensis zone in ascending order the four conodont zones can be correlated with those recognized previously in bathyal carbonate and lime chert sequences on the basis of the correlation we identified the guadalupian lopingian g l geochronostratigraphic boundary i e the basal boundary of lopingian series in the permian six radiolarian zones were also recognized in the same section namely pseudoalbaillella longtanensis zone pseudoalbaillella globosa zone follicucullus monacanthus zone follicucullus scholasticus zone follicucullus charveti zone and albaillella levis zone in ascending order correlations between radiolarian zones and conodont zones are shown here the ecological evolutionary process of conodonts and radiolarians changed abruptly through the inferred g l geochronostratigraphic boundary besides these a geochemical anomalous zone with the higher ce ce values occurred underlying the g l geochronostratigraphic boundary and petrological diagnoses around the g l boundary changed the abrupt change of ecological evolution in coincidence with the geochemical anomalous zone and change of petrological diagnoses might show the pre lopingian catastrophic event of marine faunas the reason of the event of marine faunas may be that a regression occurred at the end of the guadalupian

the contrasting biogeochemistry of iron and manganese in the pacific ocean abstract vertical and horizontal distributions of dissolved and suspended particulate fe and mn and vertical fluxes of these metals obtained with sediment traps were determined throughout the pacific ocean in general dissolved fe is low in surface and deep waters 0 1 to 0 7 nmol kg with maxima associated with the intermediate depth oxygen minimum zone 2 0 to 6 6 nmol kg vertical distributions of dissolved mn are similar to previous reports exhibiting a surface maximum a subsurface minimum a mn maximum layer coincident with the oxygen minimum zone and lowest values in deep waters near shore removal processes are more intense for dissolved fe than for dissolved mn dissolved mn in the surface mixed layer remains elevated much farther offshore than dissolved fe elevated near surface dissolved mn concentrations occur in the north pacific equatorial current suggesting transport from the eastern boundary near surface mixed layer dissolved mn concentrations are higher in the north pacific gyre reflecting enhanced northern hemisphere aeolian sources residence time estimates for the settling of refractory paniculate fe and mn from the upper water column are 62 220 days fe and 105 235 days mn in contrast residence times for the scavenging of dissolved fe and mn are 2 13 years fe and 3 74 years mn scavenging residence times for dissolved mn based on horizontal mixing in the surface mixed layer of the northeast pacific are 0 4 years nearshore to 19 years 1000 km offshore there is no evidence for in situ fe redox dissolution within sub oxic waters in the eastern tropical north pacific dissolved fe appeared to be controlled by dissolution from sub oxic sediments with oxidative scavenging in the water column or upper sediment layers however in situ mn dissolution within the oxygen minimum zone was evident

geochemical characteristics and depositional environments of cherts and associated rocks in the franciscan and shimanto terranes abstract analyses of 122 jurassic cretaceous rock samples from the franciscan terrane california and 24 cretaceous samples from the shimanto terrane southwest japan show that the cherts and associated rocks accompanied by pillow basalts are enriched in fe and mn which may have been derived from hydrothermal activities the results of the fraction analyses for terrigenous basaltic hydrothermal and biogenic end members in the franciscan rocks show that hydrothermal emanations caused iron and manganese enrichment in the rock samples and played an important role in the formation of siliceous rocks vertical variations of the hydrothermal fraction and tio2 normalized values for hydrothermal elements such as fe mn ni zn y and pb show a possibility that the bedded cherts of the franciscan terrane were deposited in a hydrothermal field on or near some active oceanic ridge for more than 30 ma and were a remnant slice of oceanic crust added to the north american continent on the other hand from the field occurrences and vertical variations of tio2 normalized values of hydrothermal elements the shimanto rocks are inferred to have been deposited in a hemipelagic environment such as marginal and inter arc basins

geochemistry of the rare earth elements in ferromanganese nodules from domes site a northern equatorial pacific abstract the distribution of rare earth elements ree in ferromanganese nodules from domes site a has been determined by instrumental neutron activation methods the concentrations of the ree vary markedly low concentrations characterize samples from a depression the valley in which quaternary sediments are thin or absent high concentrations are found in samples from the surrounding abyssal hills the highlands where the quaternary sediment section is relatively thick moreover the valley nodules are strongly depleted in the light trivalent ree lree and ce compared with nodules from the highlands some of the former showing negative ce anomalies the ree abundances in the nodules are strongly influenced by the ree abundances in coexisting bottom water some controls on the ree chemistry of bottom waters include a the more effective removal of the lree relative to the hree from seawater because of the greater degree of complexation of the latter elements with seawater ligands b the very efficient oxidative scavenging of ce on particle surfaces in seawater and c the strong depletion of both ce and the lree in or a larger benthic flux of the hree into the antarctic bottom water aabw which flows through the valley the distinctive ree chemistry of valley nodules is a function of their growth from geochemically evolved aabw in contrast the ree chemistry of highland nodules indicates growth from a local less evolved seawater source

rare earth elements in river waters we measured rare earth element ree concentrations in river waters to characterize the suspended and dissolved river flux of the ree to the oceans the ree pattern of river suspended materials is sensitive to drainage basin geology a positive correlation is observed between la yb ratios and nd model ages for the rivers studied major rivers have light ree enriched patterns relative to the north american shale composite nasc with la yb n 1 6 2 7 river water dissolved material 0 2 m is heavy ree enriched relative to suspended material and the most pronounced negative ce anomalies occur in rivers of high ph light ree concentrations vary by approximately 3 orders of magnitude and are inversely related to ph and major cation concentrations from these data we estimate that typical major river runoff has heavy ree depleted suspended material with la yb n 1 9 we conclude that the terrigenous input to the oceans from major rivers is heavy ree depleted relative to shales from the available data average river water dissolved material appears to be heavy ree enriched with la yb n 0 4 estuarine removal processes lower the dissolved ree river flux by approximately 60 and result in a flux that is more heavy ree enriched with la yb n 0 2 calculated oceanic residence times with respect to river input range from 2300 to 21 000 years are shortest for ce and greatest for the heavy ree and la such long residence times may suggest the presence of additional sources of ree in seawater

origin of basal dolomitic claystone in the marsili basin tyrrhenian sea abstract red brown dolomitic claystones overlay the marsili basin basaltic basement at odp site 650 sequential leaching experiments reveal that most of the elements considered to have a hydrothermal or hydrogenous origin in a marine environment such as fe cu zn pb co ni are present mainly in the aluminosilicate fraction of the dolomitic claystones their vertical distribution content and partitioning chemistry of trace elements and ree patterns suggest enhanced terrigenous input during dolomite formation but no significant hydrothermal influence from the underlying basaltic basement positive correlations in the c and o isotopes in the dolomites reflect complex conditions during the dolomitization the stable isotopes can be controlled in part by temperature variations during the dolomitization majority of the samples however form a trend that is steeper than expected for only temperature control on the c and o isotopes the latter indicates possible isotopic heterogeneity in the proto carbonate that can be related to arid climatic conditions during the formation of the basal dolomitic claystones in addition the dolostones stable isotopic characteristics can be influenced by diagenetic release of heavier 18o from clay dehydration and or alteration of siliciclastic material strontium and pb isotopic data reveal that the non carbonate fraction the dye of the dolomitic claystones is controlled by saharan dust 75 80 and by material with isotopic characteristics similar to the aeolian arc volcanoes 20 25 the non carbonate fraction of the calcareous ooze overlying the dolomitic claystones has a sr and pb isotopic composition identical to that of the dolomitic claystones indicating that no change in the input sources to the sedimentary basin occurred during and after the dolomitization event combination of climato tectonic factors most probably resulted in suitable conditions for dolomitization in the marsili and the nearby vavilov basins the basal dolomitic claystone sequence was formed at the initiation of the opening of the marsili basin 2 ma which coincided with the consecutive glacial stage the glaciation caused arid climate and enhanced evaporation that possibly contributed to the stable isotope variations in the proto carbonate the conductive cooling of the young lithosphere produced high heat flow in the region causing low temperature passive convection of pore waters in the basal calcareous sediment we suggest that this pumping process was the major dolomitization mechanism since it is capable of driving large volumes of seawater the source of mg2 through the sediment the red brown hue of the dolomitic claystones is terrigenous contribution of the glacially induced high eolian influx and was not hydrothermally derived from the underlying basaltic basement the detailed geochemical investigation of the basal dolomitic sequence indicates that the dolomitization was most probably related to complex tectono climatic conditions set by the initial opening stages of the marsili basin and glaciation

geochemical fractionation between porcellanite and host sediment abstract to reveal chemical fractionation during porcellanitization we have examined chemical compositions of porcellanite clasts and their host sediments from dsdp sites 164 and 166 porcellanite is an intermediate product during chert formation distinctly higher si ti ratios are observed in porcellanite relative to the host sediment indicating si transfer from the host sediment however ti normalized values of al fe mn ca na k p rare earth elements sc rb y cs pb th and cr in porcellanite are similar to those of the host sediment showing that these elements are affected by only very limited fractionation during porcellanitization and retain information about the sedimentary environment the si ti p ti and al ti ratios in dsdp clayey samples fluctuate synchronously with their sedimentation ages because the si ti and p ti ratios in clayey sediment reflect the contribution of biogenic siliceous and phosphatic debris respectively their high values in cenozoic clayey sediments indicate

the behaviour of the rare earth elements during mixing of river and sea waters rare earth element concentrations have been measured in organic rich luce river water and coastal sea water concentrations e g 350 1850 pmol kg nd in the water of luce and 45 350 pmol kg nd in luce bay are related to the presence of particles with 30 60 of the ree associated with 0 4 0 7 m particles and to riverine fe concentrations ree fractionation occurs in the river water the submicrometre river water is heavy ree enriched whereas the coarser fraction has a more shale like ree pattern laboratory experiments show that the ree in organic rich river waters are chiefly associated with feorganic matter colloids which flocculate during estuarine mixing preferential removal of heavy ree 95 relative to light ree 60 occurs but no ce anomaly is developed in contrast no ree removal occurs during estuarine mixing with organic poor river water

middle upper ordovician radiolarians in hunan and jiangxi provinces south china implications for the sedimentary environment and nature of the nanhua basin abstract the yanxi and duiershi formations of the middle upper ordovician in south china are composed of black grayish black and dark gray thin bedded cherts and siliceous slates rich in carbonaceous materials and pyrite horizontal beddings are developed the strata contain randomly distributed fossils radiolarians are discovered in the loudi yongzhou hengyang ji an and ganzhou sections the radiolaria from two sections are identified as protoentactinia sp abundances of radiolarian in the central area of hunan and jiangxi provinces are higher than in the southern area the strata become thickened while the amounts of siliceous materials are decreased and argillaceous contents are increased from northwest to southwest for the yanxi and duiershi formations the lithology gradually changes from carbonate rocks in the north to clastic rocks in the south 30si values of chert and siliceous slate range from 0 6 to 1 18 with al2o3 al2o3 fe2o3 mno tio2 lan cen ce ce and la yb n ratios of 0 65 0 97 0 01 0 16 0 99 1 27 0 85 1 10 and 0 91 1 66 respectively the sio2 and tio2 average contents are 89 08 and 0 27 the sio2 contents decrease while the tio2 increase from northwest to southeast they have similar the ree concentration with no obvious eu anomalies the yanxi and duiershi formations were deposited predominately in a bathyal environment on the continental slope basin and the seawater was stagnant in the middle early late ordovician the nanhua basin occupied a rather large area and sedimentary rocks in the region around hengyang ji an were deposited in the basin center with terrigenous source derived from the southeast

chert geochemistry depositional setting stratigraphic and structural significance for the permian nong pong formation khao khwang fold and thrust belt saraburi thailand abstract the deepwater chert shale limestone tuff permian nong pong formation npf of the saraburi group is a major unit within the triassic indosinian orogeny khao khwang fold and thrust belt kkftb whether the npf was deposited in a continental margin or ocean basin remains uncertain and impacts structural sedimentary and stratigraphic interpretations of the kkftb this study investigates chert geochemistry from a 60 m section of the formation near muak lek town to determine its depositional environment radiolarian fauna from the chert beds includes follicucullus porrectus rudenko probable late guadalupian late middle permian indicating the npf is time equivalent to adjacent carbonate platform deposition khao khwang and khao khad formations high ratios of sio2 sio2 al2o3 fe2o3 and fe al mn plots indicate a biogenic origin radiolarians sponge spicules for the cherts far from a hydrothermal source trace element ratios for u th sc th and sr ba and ce anomalies in the nasc normalized ree distribution are ambiguous and range between shallow to deep ocean basin and continental margin settings major elements analysis of cherts show 1 high ratios of sio2 sio2 al2o3 fe2o3 range 0 60 0 82 0 76 average 2 al al fe mn range 0 67 0 82 and 3 average mno tio2 0 14 the mno tio2 and al2o3 al2o3 fe2o3 ratio 100 fe2o3 sio2 vs 100 al2o3 sio2 and fe2o3 100 sio2 vs al2o3 100 sio2 diagrams indicate deposition on a continental margin the lan cen versus al2o3 al2o3 fe2o3 discrimination diagram indicates a pelagic continental margin setting combined geochemical structural and sedimentary facies analyses suggests the npf was deposited in a deep marine normal fault bounded basin on a rifted ribbon continent margin where carbonate platforms grew on structural highs

geochemical characteristics and geological significance of the bedded chert during the ordovician and silurian transition in the shizhu area chongqing south china a large amount of bedded chert widely deposited during the ordovician and silurian transition in south china in this study analyses of the petrographic characteristics the major elements and rare earth elements rees were conducted on 31 bedded chert samples obtained from the wufeng and longmaxi formations at the qiliao section in the shizhu area of the sichuan basin to determine the sedimentary environment and the origin of the bedded chert during the ordovician and silurian transition the following conclusions were obtained 1 the bedded chert in the wufeng and longmaxi formations at the qiliao section originated mainly from terrigenous input and siliceous organisms and suffered slightly influence in hydrothermal fluid 2 siliceous organisms was a key factor controlling the differences in the sio2 content of the bedded chert in the wufeng and longmaxi formations at the qiliao section and 3 the bedded chert in the wufeng and longmaxi formations deposited in a continental margin environment d

the effect of hydrothermal processes on midwater phosphorus distributions in the northeast pacific abstract the distributions of dissolved particulate and sedimentary phosphorus were measured in the region of the juan de fuca ridge to determine the impacts of hydrothermal processes on the phosphorus cycle in the oceans significant negative dissolved phosphate anomalies ranging from 0 to 60 nmol l were observed in the water column at depths between 1900 and 2300 db the largest anomalies

geochemistry of late permian to early triassic pelagic cherts from southwest japan implications for an oceanic redox change major trace and rare earth element abundances were determined for the southwestern japanese pelagic chert sequence from the early late permian to early early triassic to investigate a redox change in deep sea pelagic environments before and at the permo triassic boundary ptb 251 ma the sequence was primarily deposited in the deep sea of the superocean panthalassa and then was accreted to japan in the middle jurassic a remarkable lithostratigraphic change from red chert to siliceous carbonaceous claystone through gray chert is observed in this sequence constituent elements for these sedimentary rocks are essentially derived from two sources 1 an ancient seawater via biogenic mainly radiolarian hydrothermal and authigenic materials and 2 an average shale like terrigenous material the present measurement demonstrates significant stratigraphic changes of the ce cenon ter value estimated ce anomaly value of non terrigenous component recalculated by subtraction of terrigenous rees from bulk rees and the mn te sample mn te paas value excess mn component other than terrigenous one te terrigenous elements including ti al nb hf th paas post archean average australian shale in the permian chert the ce cenon ter values increase from 0 2 to 1 and the mn te sample mn te paas values decrease up section suggesting that the redox condition of deep sea open ocean changed from oxic to suboxic in an interval of approximately 10 myr the fe te sample fe te paas and mn te sample mn te paas values of carbonaceous claystone near or at the ptb are less than unity suggesting that reductive dissolution of iron and manganese occurred under an anoxic condition this supports the idea of the ptb oceanic anoxia in the superocean panthalassa the present data suggest that the anoxic condition prevailed in the deep sea pelagic regions for an extremely long period much more than 10 myr from the middle late permian to early early triassic this long term development of widespread oceanic anoxia may have been linked to the greatest mass extinction of the phanerozoic

rare earth element systematics in hydrothermal fluids abstract rare earth element concentrations have been measured in hydrothermal solutions from geothermal fields in italy dominica valles caldera salton sea and the mid atlantic ridge the measured abundances show that hydrothermal activity is not expected to affect the ree balance of either continental or oceanic rocks the ree enrichment of the solutions increases when the ph decreases high temperature solutions 230 c percolating through different rock types may show similar ree patterns

anomalies in rare earth distributions in seawater gd and tb we have measured profiles of the rare earth elements ree in atlantic and pacific ocean waters the data normalized versus shales exhibit a pronounced anomaly in gd relative to its neighbors eu and tb in the ree series such that the gd concentrations are high by 30 50 closer inspection reveals that the anomaly is made up of both elevated gd and depressed tb concentrations likely associated with solution chemistry shifts in the transition from an exactly half filled 4f electron shell anomalies in gd and tb solution complexation are also indicated by the turner whitfield dickson speciation model the overall trend of heavy ree iii enrichment in seawater and the gdtb anomaly described here tend to support scavenging as an important removal mechanism for the ree from seawater

paleoredox variations in ancient oceans recorded by rare earth elements in fossil apatite abstract rare earth element concentrations in biogenic apatite of conodonts fish debris and inarticulate brachiopods were determined in over 200 samples from cambrian to modern sediments tests for experimental bias caused by the chemicals used to separate fossils from the rock matrix and for interlaboratory interexperiment or interspecies related variations clearly show that no resolvable fractionation of ree occurs incorporation of ree in biogenic apatite of recent fish debris occurs near the sediment water interface soon after deposition and reflects characteristics of seawater the original ree signature apparently survives subsequent burial and diagenesis cerium variations in fish debris from modern environments are controlled by redox potential ce is fractionated by co precipitation with metallic oxides under oxidizing conditions this fractionation produces a negative ce anomaly ce anom in seawater that is reflected in the sedimented fish debris conversely no fractionation of ce occurs under reducing conditions resulting in ce concentrations that are normal to enriched in anoxic seawater and fish debris deposited under local or basinwide anoxic conditions extrapolation of observations of the redox control of ce anom in modern oceans to fossil apatite indicates that anoxic conditions were prevalent in lower paleozoic and lower triassic oceans whereas in the upper paleozoic the world ocean was generally oxidizing

use of seasat synthetic aperture radar and landsat multispectral scanner subsystem data for alaskan glaciology studies seasat synthetic aperture radar sar and landsat multispectral scanner subsystem mss data of three areas in alaska were studied in order to determine what hydrological information could be extracted using digital data from both sensors the first area is located in northern alaska and contains numerous thaw lakes the other areas contain valley glaciers in the alaska range and a piedmont glacier malaspina in south central and southern alaska respectively sar and mss subscenes of the thaw lakes and subscenes of the malaspina glacier were digitally registered registration of the data in the alaska range study area was not feasible due to a lack of sufficient tie points resulting from shadowing and layover effects in the sar data results of the data obtained from the thaw lake study area showed that the location and identification of some older remnant lake basins were more easily determined in the registered data using an mss sar overlay than in either sar or mss data alone separately both the sar and the mss data were useful for determination of surging glaciers based on their distinctive medial moraines and landsat data were useful for locating the glacier firn zone in the analysis of the malaspina glacier scenes the sar data were useful for locating heavily crevassed ice beneath glacial debris and landsat provided information concerning the extent of the debris overlying the glacier together the data set gave a good representation of the extent of the glacier and crevasse patterns

relation between chemical composition and sedimentation rate of pacific ocean floor sediments deposited since the middle cretaceous basic evidence for chemical constraints on depositional environments of ancient sediments chemical characteristics of pacific marine sediments were examined for different environments operating since the middle cretaceous as a result of the examinations a procedure for evaluating depositional environments of ancient sediments in orogenic belts is proposed the concentration of hydrogenous authigenic elements such as mn co and ni in sediments has a relationship to the bulk sedimentation rate similarly a new indicator which is a measure of the sedimentation rate of terrigenous lithogenic materials in sediments is proposed this indicator is expressed as the weight ratio of a hydrogenous element to tio 2 because the sedimentation rate of terrigenous materials gradually decreases with distance from land the ratio varies according to depositional environments geochemical examination of pacific dsdp materials has shown that the distribution of element ratios mno tio 2 co tio 2 and others in surface sediments of the pacific has not changed since the middle cretaceous as an

the whole rock cerium anomaly a potential indicator of eustatic sea level changes in shales of the anoxic facies abstract the whole rock cerium anomaly tested for outer shelf upper slope stratigraphic sections from the middle ordovician through the lower silurian of scotland is proposed as an empirical technique to develop a eustatic 3rd order or finer scale sea level curve this interval was chosen as it straddles the well documented late ordovician glaciation and can be defined by graptolite zones the anomaly is calculated from neutron activation analysis of low carbonate phosphate free fossil free field identified shales of the graptolite facies by comparison of the normalized cerium content with the linearized trend of the normalized composition of other rare earth elements in order of atomic number for sections originally deposited in the main pycnocline below the surface mixed layer values of the anomaly for a given sample would indicate its position on the redox curves developed for the early paleozoic by wilde 1987 changes in the anomaly that are positive with time would indicate a lowering of sea level as the apparent depth on the redox curve would reflect more oxic conditions relative changes negative with time would indicate a rise in sea level as the apparent depth reflects more anoxic conditions depending on the vertical sample spacing and the time interval sampled resolution of the order of 1 m y might be achieved thus the vail et al 1977 curves of the 3rd order 1 to 10 m y or of finer scale could be obtained by this technique with the proper choice of section accordingly for the early through middle paleozoic when the main pycnocline was anoxic this geochemical technique could be used to develop eustatic sea level curves and additionally offer an independent calibration for seismic stratigraphy as well as an indicator of glacial interglacial climatic sequences or eustatic changes due to fluctuations in global ridge crest volumes

origin of silica paleoenvironment and organic matter enrichment in the lower paleozoic niutitang and longmaxi formations of the northwestern upper yangtze plate significance for hydrocarbon exploration abstract lower paleozoic shale is an important source rock and reservoir for gas in the northwestern upper yangtze plate the paleoenvironment and its impact on organic matter enrichment of the shale plays a vital role in the exploration and development of the resource based on the analysis of the results of total organic carbon toc maceral examination bitumen reflectance rb major elements trace elements rare earth elements rees and x ray diffraction xrd of shale samples from the niutitang and longmaxi formations the origin of silica the paleoenvironment and the mode of organic matter enrichment of the shale were examined the shales of the niutitang and longmaxi formations have high toc abundance with type i organic matter and high maturity quartz and clay minerals dominate the mineral constituents leading to characterization as siliceous shale the average sio2 content of the shale in the niutitang and longmaxi formations is above 70 wt al2o3 and tfe2o3 total iron are the next most abundant major elements with average values of 12 80 wt and 1 95 wt in the niutitang formation and average values of 11 44 wt and 4 09 wt in the longmaxi formation compared with the upper continental crust ucc v mo and u are the most enriched elements the average lree hree of the shale samples is very low and the chondrite normalized ree distribution pattern shows sloping lree trends and flat hree trends towards the right the total rare earth elements of the shale vary within the range of 147 85 219 60 ppm and 159 90 222 02 ppm in both the niutitang and longmaxi formations suggesting that the shale has not been subject to obvious hydrothermal fluid activities the correlation diagrams of sio2 al2o3 sio2 toc and siexcess toc the diagrams of hydrothermal origins and the elemental parameters indicate that the silica of the shales from the niutitang and longmaxi formations are mainly of biogenic origins with a lesser contribution from terrigenous detrital sources the ratios of mno2 tio2 and al2o3 al2o3 tfe2o3 of the shale samples all show limited variability illustrating that the shales are mainly deposited on the continental margin the average chemical alteration index cia values of the niutitang and longmaxi formations are 71 25 and 72 77 with little variation and the average sr cu ratios are 4 38 and 2 22 reflecting a warm and humid paleoclimate for both formations the average ni co th u and u readings of the shale samples of the formations are 10 91 0 97 and 1 51 and 12 69 0 43 and 1 75 indicating that the redox conditions during the sedimentation of the formations were anoxic the positive correlations between toc and paleoenvironmental proxies reveal a warm and humid climate and that anoxia had a positive effect on organic matter enrichment these conditions have laid a geological foundation for the enrichment of shale gas and that the upper yangtze plate is favorable for future shale gas exploration

rare earth elements in marine sediments and geochemical standards abstract a comparison was made of sediment dissolution methods used for analysis of rare earth elements ree and major elements fe al ti zr p dissolution by hf and lithium metaborate fusion were compared in seven geochemical standards and twenty marine sediments using hf dissolution of shelf and slope sediments this author previously observed that these marine sediments were significantly depleted in heavy ree hree relative to the crustal abundance i e shale this observation plus published ree compositions of river particles lead to the conclusion that the riverine input of particles to the oceans cannot be assumed to have the crustal abundance for ree comparisons of fusion total to hf dissolutions for marine sediments show that the latter method misses between 20 and 100 of the hree i e dy er yb lu and large percentages of zr in contrast fusion and hf dissolution yield similar concentrations for the light la ce nd and middle eu gd ree and other major elements the fusion data show that the marine sediments are more similar in ree composition to shales than previously reported by this author who underestimated the contribution of hf insoluble residues to the concentration of hree the heavy mineral zircon is the most likely cause of this observation zircons known to be enriched in hree were identified by x ray diffraction as a major component of the hf insoluble residues geochemical standards also have a significant but usually smaller fraction of their hree associated with hf insoluble phases these compositional differences have significance with respect to interpreting river inputs oceanic abundances and diagenesis of ree

rare earth distributions with a positive ce anomaly in the western north atlantic ocean from the vertical distributions of the rare earth elements ree in the sargasso sea we now report the first profiles of pr tb ho tm and lu in seawater together with profiles for la ce sm eu and yb the first observations of positive ce anomalies in seawater are ascribed to reducing inshore sediments as a source for ce ref 1 all vertical profiles are consistent with adsorption of trivalent rare earths by settling particles possibly siliceous or calcareous followed by their release at or near the sea floor on dissolution of the carriers the very different ce profile demonstrates the additional effects of oxidation reduction reactions

magnetostratigraphy and sedimentology of the jingchuan red clay section and correlation of the tertiary eolian red clay sediments of the chinese loess plateau a 325 m thick loess and red clay sequence was recently discovered at jingchuan which is situated about 45 km north of the previously studied lingtai section in the middle part of the chinese loess plateau the jingchuan section is composed of 199 m of pleistocene loess and 126 m of tertiary red clay deposits paleomagnetic studies show that the jingchuan red clay has a basal age of at least 7 7 ma which represents the oldest red clay deposits presently known in the loess plateau field observations and grain size analyses both suggest an eolian origin of the red clay thus extending available records of the eolian deposits in the loess plateau from about 7 0 ma to 7 7 ma correlation of both pedostratigraphy and magnetic susceptibility records suggests that the late cenozoic red clay records in the loess plateau have a general continuous nature thereby providing potential for deriving long term climatic evolution signals from this eolian loess and red clay sequence

rare earth elements and neodymium isotopes in ferromanganese oxide coatings of cenozoic foraminifera from the atlantic ocean abstract an evaluation has been made of the method of establishing the ree contents and patterns and nd isotopic compositions of sea water over cenozoic time from their record in the femn oxide coatings of foraminiferal calcite using 0 60 ma samples from the rio grande rise dsdp site 357 it has been established that the ree contents of the coatings are generally similar to those of recent samples however in the cenozoic samples the surface coatings have been diagenetically modified under suboxic conditions resulting in a distinctly different ree pattern although the original 143 nd 144 nd ratios appear to have been preserved the nd isotopic curve for cenozoic sea water in the s atlantic shows clear temporal trends although these are not so extreme as to show 143 nd 144 nd ratios outside the range observed in modem sea water with the principal exception of the oldest samples there is an approximate inverse relationship between the nd and sr isotopic compositions of the foraminifera it is suggested that the changes reflect both global changes in the relative proportions of nd and sr derived from continental input and from the weathering of volcanic debris together with short term and local variations to which the sr curve is insensitive reflecting the different response times of the two elements to changes in oceanic input functions the nd isotope curve appears to be a potentially useful tracer of ocean palaeochemistry

rare earth element geochemistry of standard sediments a study using inductively coupled plasma spectrometry the rare earth elements ree and y have been determined in 15 international standard sediments from france german democratic republic canada and the u s a samples were prepared using conventional rock dissolution techniques and the ree and y were separated from other constituents using cation exchange chromatography the ree la ce pr nd sm eu gd dy ho er yb lu and y were analysed simultaneously by inductively coupled plasma atomic emission spectrometry results indicate that u s g s standard shale sco 1 cody shale is a good reference material to use for the normalisation of the ree distributions of sediments data normalised to sco 1 are more readily interpreted than those normalised to existing estimates of average shale the ree patterns of standard sediments vary considerably in shape span an order of magnitude in absolute concentration and provide valuable reference values for the ree analysis of other sedimentary materials

age and origin of the mafic rocks and radiolarian cherts within the ne jiangxi ophiolite melange implications for the tectonic evolution of se china

cerium a chemical tracer for paleo oceanic redox conditions abstract the ce anomalies found in marine carbonates provide a sensitive indicator for the study of paleo oceanic redox conditions the dependency of cce the observed ce concentration and cepo04 the activity of the cepo4 complex to the po2 ph and pco2 of seawater can be used for deciphering some aspects of the paleo ocean chemistry and is log c ce log cepo 0 4 13 2 0 25 log p o 2 3 0 ph 1 95 0 25 log p o 2 1 50 log p co 2 1 50 log ca the ph which is related to pco2 and po2 are major factors for controlling the ce concentration in seawater therefore ce anomalies ceas ce observed ce interpolated between la and pr or nd serve as indicators for ph or pco2 or po2 changes nearly uniform ce abundances found in pacific 5000 m water columns piepgras and jacobsen 1988 and the ceas in ichthyoliths can be explained using this model a general cea shift in sediments from d s d p holes 525a 530a b 516 516f suggest that the entire south atlantic water redox condition changed from reducing to oxidizing at 56 my in the north atlantic the galicia margin samples show a redox change between 132 148 my indicating active surface currents between the atlantic ocean and the shallow sea off the iberian peninsula the carbonate samples from d s d p hole 316 in the central pacific yielded an average cea of 0 15 0 01 which is 2 3 the ceas observed in deep pacific seawater by piepgras and jacobsen 1988 the relative enrichment of ce in these samples is ascribed to coprecipitation of ce oh 4 onto fe mn o coatings the striking similarities in the trace element profiles of ree sc hf th and ceas and the low u abundances 0 08 ppm in many marine carbonates indicate insignificant ce redox and trace elemental concentration changes for the pacific ocean over the past 95 my no significant ce redox change occurred in the pacific ocean within k t boundary one 240 my china limestone deposited under oxic sedimentary conditions yielded a cea of 0 53 calculations indicate a pco2 of 1 9 present value prevailed over the 240 my tethyan ocean u th ratios and low u concentrations are diagnostic indicators for obtaining reliable ceas in marine carbonates and perhaps for biogenic apatites and conodonts as well

rare earth elements in saanich inlet british columbia a seasonally anoxic basin rare earth element and manganese distributions have been investigated in saanich inlet british columbia a seasonally anoxic basin redox cycling of ce and mn takes place across an oxic suboxic boundary approximately 20 m shallower than the o2h2s interface the remaining strictly trivalent ree undergo scavenging above this oxic suboxic boundary and regeneration from dissolving host phases below it these processes result in pronounced removal of ce from solution above the oxic suboxic boundary due to oxidative precipitation along with preferential uptake of the lighter trivalent ree during scavenging below the oxic suboxic boundary regeneration of particulate ree into solution leads to a less pronounced ce depletion and a less pronounced hree enrichment in the anoxic bottom waters dissolved ree concentrations in the sediment pore waters exhibit an approximately ten fold increase across the seawater sediment interface but then decrease with increasing depth indicating removal from solution during later diagenesis calculated diffusive fluxes of the ree and mn from the sediments into the overlying anoxic water column are insufficient to account for the accumulated trace metal enrichments observed in the water column we propose an annual redox cycle for saanich inlet in which flushing causes extensive oxidative precipitation and scavenging of trace elements from the water column each autumn the same material is rapidly regenerated from the underlying near surface sediments when the basin next turns anoxic

rare earth major and trace elements in chert from the franciscan complex and monterey group california assessing ree sources to fine grained marine sediments abstract rare earth element ree major and trace element analyses of 77 samples from the mesozoic franciscan complex and miocene monterey group of california usa indicate that magnitudes of the ce anomaly ce ce and total ree abundances sree in these rocks are controlled dominantly by a the amount of included metalliferous material b the amount of direct terrigenous input and c the overall burial rate the relative importance of these individual processes varies across an ocean basin in such a way that ree relative fractionations and sree correspond with its depositional environment our conclusions are supported by an extensive review of published ree data from various river coastal open ocean and ridge influenced waters as well as terrigenous pelagic and metalliferous sediment the chert sequences record deposition in spreading ridge open ocean basin and continental margin environments the relative importance of metalliferous and terrigenous influences and the role of scavenging from seawater may be estimated from a sample s inferred depositional distance km from the spreading ridge the major element chemistry and the stratigraphie context the ce ce values are low 0 29 in the vicinity of spreading ridges and trend to successively higher 1 values with decreasing metalliferous and increasing terrigenous influences other ree indicators ree lu n la n eu eu also respond to metalliferous and terrigenous influences near the spreading ridge chert ree appears determined by burial rate while shale ree responds to metalliferous abundance in open ocean and continental margin environments ree is controlled by sediment exposure time and therefore is related inversely to burial rate ree data are consistent with the major elements fe2o3 mno and al2o3 in reflecting the respective metalliferous and terrigenous sources p2o5 and cao do not vary with ce ce in any environment but cao shows a weak negative correlation with ree trace element trends e g v cr cu ge si rb sr y th u in general can similarly be accounted for in the context of depositional position relative to metalliferous and terrigenous inputs rees in chert appear less affected by post depositional processes than either major or trace elements indicating that rees are better tools for paleoceanographic or tectonic reconstructions that are based on chert chemistry this work complements recent efforts to elucidate the factors determining large scale ree distributions in marine sediments and has direct bearing on previous attempts to use the ce anomaly in older rocks and sediments as a recorder of secular variations and anoxic events in the overlying water column

integration of bed characteristics geochemical tracers current measurements and numerical modeling for assessing the provenance of beach sand in the san francisco bay coastal system abstract over 150 million m3 of sand sized sediment has disappeared from the central region of the san francisco bay coastal system during the last half century this enormous loss may reflect numerous anthropogenic influences such as watershed damming bay fill development aggregate mining and dredging the reduction in bay sediment also appears to be linked to a reduction in sediment supply and recent widespread erosion of adjacent beaches wetlands and submarine environments a unique multi faceted provenance study was performed to definitively establish the primary sources sinks and transport pathways of beach sized sand in the region thereby identifying the activities and processes that directly limit supply to the outer coast this integrative program is based on comprehensive surficial sediment sampling of the san francisco bay coastal system including the seabed bay floor area beaches adjacent rock units and major drainages analyses of sample morphometrics and biological composition e g foraminifera were then integrated with a suite of tracers including 87sr 86sr and 143nd 144nd isotopes rare earth elements semi quantitative x ray diffraction mineralogy and heavy minerals and with process based numerical modeling in situ current measurements and bedform asymmetry to robustly determine the provenance of beach sized sand in the region

ree fe variations in hydrothermal sediments implications for the ree content of seawater seafloor hydrothermal vent solutions exhibit rare earth element ree enrichments ranging between one to three orders of magnitude greater than average seawater to assess the impact of these hydrothermal inputs on ocean chemistry we have examined the behavior of rees for hydrothermal sediments collected adjacent to two pacific spreading ridge sites the east pacific rise at 19 s and the southern juan de fuca ridge at 4s n in general the ree fe ratios for both proximal and distal hydrothermal sediments are greater than vent solutions by a factor of 2 to 500 and these ratios increase with increasing distance away from the ridge axis an evaluation of these results in the context of previous models of ree behavior indicates that in fact seawater experiences a net depletion in rees as a result of hydrothermal activity this is due primarily to the large scavenging capacity of iron oxyhydroxides which precipitate from these solutions such an interpretation explains why the ree content of seawater collected in the vicinity of hydrothermal vents is anomalously lower than normal seawater sampled from a comparable depth

late cenozoic ge si record of marine biogenic opal implications for variations of riverine fluxes to the ocean we have determined germanium silicon ratios in purified diatoms and radiolarians from siliceous sediments in holocene core tops one late pleistocene piston core and four high latitude southern ocean deep sea drilling project dsdp sites ranging in age from holocene to oligocene high latitude holocene diatoms in the 10 to 38 m size fraction ge si opal 0 693 0 039 10 6 faithfully record the present oceanic ratio ge si seawater 0 699 0 004 10 6 this confirms that diatoms from siliceous oozes are monitors of seawater ge si and may record past changes in rates of delivery of weathering products to the sea from continental and seafloor weathering large diatoms and radiolarians display ratios much lower than ge si seawater suggesting that ge si opal to some extent displays the effects of biological fractionation from 0 to 2 5 m y b p ge si opal in diatoms from dsdp sites ranges from about 0 54 to 0 70 10 6 similar to the range observed in one late pleistocene piston core over the last 25 kyr from 2 5 to 6 m y b p the ratio is more variable while prior to 10 m y b p ratios are clearly higher averaging about 0 9 10 6 in the early to middle miocene low values of the ratio are consistent with global weathering regimes dominated by river silica input to the sea while higher ratios suggest periods of enhanced hydrothermal input or reduced fluvial contribution nevertheless an oceanic one box model with variable river and hydrothermal inputs and biogenic opal output cannot adequately account for the magnitude or the timing of changes observed in the record suggesting the existence of other sources sinks for inorganic germanium and or silicon to or from the sea

regional variations of ree patterns in sediments from active plate boundaries abstract about 150 sediment samples from mid ocean ridges east pacific rise central indian ocean ridge carlsberg ridge and the red sea and from a back arc spreading environment lau basin were analyzed by instrumental neutron activation a ratio method for rare earth elements involving a plot of elemental ratios of ce la and la yb is proposed to characterize marine sediments in the characterization plot east pacific rise and lau basin sediments occupy distinct fields in the plot suggesting hydrothermal overprint while sediments from the central indian ocean and the carlsberg ridge plot into the field for normal deep sea sediments