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PubMed1994

Sm-Nd dating of Fig Tree clay minerals of the Barberton greenstone belt, South Africa.

Sm-Nd isotopic data from carbonate-derived clay minerals of the 3.22-3.25 Ga Fig Tree Group, Barberton greenstone belt, South Africa, form a linear array corresponding to an age of 3102 +/- 64 Ma, making these minerals the oldest dated clays on Earth. The obtained age is 120-160 m.y. younger than the depositional age determined by zircon geochronology. Nd model ages for the clays range from approximately 3.39 to 3.44 Ga and almost cover the age variation of the Barberton greenstone belt rocks, consistent with independent evidence that the clay minerals are derived from material of the belt. The combined isotopic and mineralogical data provide evidence for a cryptic thermal overprint in the sediments of the belt. However, the highest temperature reached by the samples since the time of clay-mineral formation was <300 degrees C, lower than virtually any known early Archean supracrustal sequence.

Aluminum Silicates↗
PubMedDate not supplied

Observations of large-amplitude cross-shore internal bores near the shelf break, Santa Monica Bay, CA.

Two sets of moorings were deployed along a cross-shelf transect in central Santa Monica bay for four months in the winter of 1998-1999. Both sites had an array of instruments attached to tripods set on the seafloor to monitor currents over the entire water column, surface waves, near-bed temperature, water clarity and suspended sediment. A companion mooring had temperature sensors spaced approximately 10 m apart to measure temperature profiles between the surface and the seafloor. One array was deployed in 70 m of water at a site adjacent to the shelf break, just northwest of a major ocean outfall. The other was deployed on the mid shelf in 35 m of water approximately 6 km from the shelf break site. The subtidal currents in the region flowed parallel to the isobaths with fluctuating time scales around 10 days, a typical coastal-ocean pattern. However, during the falling phase of the barotropic spring tide, sets of large-amplitude, sheared cross-shore current pulses with a duration of 2-5 h were observed at the shelf break site. Currents in these pulses flowed exclusively offshore in a thin layer near the bed with amplitudes reaching 30-40 cm/s. Simultaneously, currents with amplitudes around 15-20 cm/s flowed exclusively onshore in the thicker layer between the offshore flow layer and the sea surface. The net offshore transport was about half the onshore transport. Near-surface isotherms were depressed 30-40 m. These pulses were likely internal bores generated by tidal currents. Bed stresses associated with these events exceeded 3 dynes/cm(2). These amplitudes are large enough to resuspend and transport not only fine-grained material, but also medium to coarse sands from the shelf toward the slope. Consequently, the seafloor over the shelf break was swept clear of fine sediments. The data suggest that the internal bores dissipate and are reduced in amplitude as they propagate across this relatively narrow shelf. There is evidence that they reach the 35 m site, but other coastal ocean processes obscure their distinctive characteristics.

California↗
PubMed2003

Microbial communities associated with geological horizons in coastal subseafloor sediments from the sea of okhotsk.

Microbial communities from a subseafloor sediment core from the southwestern Sea of Okhotsk were evaluated by performing both cultivation-dependent and cultivation-independent (molecular) analyses. The core, which extended 58.1 m below the seafloor, was composed of pelagic clays with several volcanic ash layers containing fine pumice grains. Direct cell counting and quantitative PCR analysis of archaeal and bacterial 16S rRNA gene fragments indicated that the bacterial populations in the ash layers were approximately 2 to 10 times larger than those in the clays. Partial sequences of 1,210 rRNA gene clones revealed that there were qualitative differences in the microbial communities from the two different types of layers. Two phylogenetically distinct archaeal assemblages in the Crenarchaeota, the miscellaneous crenarchaeotic group and the deep-sea archaeal group, were the most predominant archaeal 16S rRNA gene components in the ash layers and the pelagic clays, respectively. Clones of 16S rRNA gene sequences from members of the gamma subclass of the class Proteobacteria dominated the ash layers, whereas sequences from members of the candidate division OP9 and the green nonsulfur bacteria dominated the pelagic clay environments. Molecular (16S rRNA gene sequence) analysis of 181 isolated colonies revealed that there was regional proliferation of viable heterotrophic mesophiles in the volcanic ash layers, along with some gram-positive bacteria and actinobacteria. The porous ash layers, which ranged in age from tens of thousands of years to hundreds of thousands of years, thus appear to be discrete microbial habitats within the coastal subseafloor clay sediment, which are capable of harboring microbial communities that are very distinct from the communities in the more abundant pelagic clays.

Colony Count, Microbial↗
PubMed2003

Arsenic pollution in groundwater: a self-organizing complex geochemical process in the deltaic sedimentary environment, Bangladesh.

The presence of considerable concentrations of As (Sonargon: below detection limit (bdl)-1.46 mg/l; Faridpur: bdl-1.66 mg/l) and some other elements (like B, F, U) in groundwater of the Ganges-Meghna-Brahmaputra (G-M-B) rivers flood plain indicate that several millions of people are consuming contaminated water. Conditions regulating the mobilization and diagenetic behavior of arsenic in sediments are not well characterized, although understanding these conditions is essential in order to predict the modes of transfer of this contaminant from sediments to groundwater. Analyses of vertical profiles of total arsenic and iron as well as easily soluble As and reducible (reactive) iron concentrations in sediments of the Ganges and Meghna flood plains show no arsenic-enriched layer up to 36-m depth. However, arsenic content in sediments is relatively higher than mean crustal concentration, showing some peaks (Sonargaon: 27.9 mg/kg; 3 m, 31.5 mg/kg; 9 m, 27.30 mg/kg; 16 m, 37.70 mg/kg; 29.5 m, Faridpur: 19.80 mg/kg; 6 m, 26.60 mg/kg; 14.5 m, 29.40 mg/kg; 25 m) depending on the periodical differences in sedimentary cycling of arsenic, metal (hydr)oxides and organic matter. Seasonal changes have no clear or consistent effect on the groundwater arsenic concentrations; with the exception of a small-scale localized irregular change (10-16%). However, easily reducible metal oxides and hydroxides were significant factors affecting the retention of arsenic by sediments during leaching. The biogeochemical cycling of arsenic and iron is closely coupled in deltaic systems where iron oxy-hydroxides provide a carrier phase for the deposition of arsenic in sediments. Analytical results of mimic leaching experiments strongly supported the reduction (Fe oxy-hydroxides) mechanism for arsenic mobilization in alluvial aquifer of deltaic sedimentary environment of G-M-B rivers flood plain.

Arsenic↗
PubMed2006

Luminescence dating of the barrier spit at Chilika Lake, Orissa, India.

Optically stimulated luminescence dating has been used to investigate the chronological development of the outer barrier spit forming Chilika Lake (Orissa, India), the largest brackish-water lagoon in Asia. Sixteen samples were examined, and these yielded equivalent doses of between 153 +/- 3 mGy and 2.23 +/- 0.07 Gy, corresponding to ages from approximately 40 y at the top of the spit to approximately 300 y at the bottom. The youngest ages are consistent with the age of the overlying vegetation, and modern material taken from the sub-tidal beach gave a dose of 4 +/- 2 mGy (corresponding to an age of 0.7 +/- 0.4 y), confirming that any previous potential luminescence signal in the source sediment is completely set to zero before incorporation into the spit. A clearly defined period of >2.5 m of barrier construction approximately 40 y ago is identified; prior to that the deposition rate was relatively constant for approximately 300 y.

Algorithms↗
PubMedDate not supplied

Clay-mineral suites, sources, and inferred dispersal routes: Southern California continental shelf.

Clay mineralogy is useful in determining the distribution, sources, and dispersal routes of fine-grained sediments. In addition, clay minerals, especially smectite, may control the degree to which contaminants are adsorbed by the sediment. We analyzed 250 shelf sediment samples, 24 river-suspended-sediment samples, and 12 river-bed samples for clay-mineral contents in the Southern California Borderland from Point Conception to the Mexico border. In addition, six samples were analyzed from the Palos Verdes Headland in order to characterize the clay minerals contributed to the offshore from that point source. The <2 microm-size fraction was isolated, Mg-saturated, and glycolated before analysis by X-ray diffraction. Semi-quantitative percentages of smectite, illite, and kaolinite plus chlorite were calculated using peak areas and standard weighting factors. Most fine-grained sediment is supplied to the shelf by rivers during major winter storms, especially during El Niño years. The largest sediment fluxes to the region are from the Santa Ynez and Santa Clara Rivers, which drain the Transverse Ranges. The mean clay-mineral suite for the entire shelf sediment data set (26% smectite, 50% illite, 24% kaolinite+chlorite) is closely comparable to that for the mean of all the rivers (31% smectite, 49% illite, 20% kaolinite+chlorite), indicating that the main source of shelf fine-grained sediments is the adjacent rivers. However, regional variations do exist and the shelf is divided into four provinces with characteristic clay-mineral suites. The means of the clay-mineral suites of the two southernmost provinces are within analytical error of the mineral suites of adjacent rivers. The next province to the north includes Santa Monica Bay and has a suite of clay minerals derived from mixing of fine-grained sediments from several sources, both from the north and south. The northernmost province clay-mineral suite matches moderately well that of the adjacent rivers, but does indicate some mixing from sources in adjacent provinces.

Aluminum Silicates↗
PubMed2003

The loading history of trace metals and nutrients in Altata-Ensenada del Pabellón, lagoon complex, northwestern Mexico.

This paper summarizes the geochemical investigations about the origin and loading history of some trace metals (Ag, Cu and Zn) and nutrients (N and P) in the coastal lagoon complex of Altata-Ensenada del Pabellón, Mexico, by using the radioactive chronometers 210Pb and 228Th and the stable isotopes of C and N. The examination of sediment cores collected at different locations in the lagoon system identified a slight enrichment in metals and nutrients in some points, which was mainly associated to organic matter accumulation. Stable C and N isotope ratios revealed wastewater inputs to the lagoon system and the 210Pb geochronology showed that anthropogenic impact started 50 years ago, with the beginning of the agriculture development and the associated urban growth of the surrounding area. Several atypical 210Pb and 228Th/232Th profiles demonstrated that biological and physical disturbances are common phenomena in these environments, that frequently mask the pollution records; and therefore, considering that the contaminated sediments at some locations in the lagoon system are frequently resuspended and re-oxygenated, the pollutants will continue to be easily remobilized in the food chain.

Animals↗
PubMed1998

A composite reference section for terminal proterozoic strata of southern Namibia.

Integrated sequence stratigraphic and chemostratigraphic data yield a framework for correlations of stratigraphic units in the terminal Proterozoic to Cambrian Witvlei and Nama Groups of Namibia. Coupled with precise U-Pb zircon age constraints, these correlations make it possible to construct a composite reference section for use in calibrating terminal Proterozoic chronostratigraphy. The Namibian reference section starts with two distinct glacial horizons and extends up to within 1 million years of the Proterozoic-Cambrian boundary. The two glacial horizons may represent each of two distinct Varanger-age glaciations better known from the North Atlantic region. From the higher of the two glacial horizons up, the composite stratigraphy preserves one of the thickest and most complete available records of carbon-isotope variability in post-Varanger terminal Proterozoic seawater. Four carbon-isotope chemostratigraphic intervals are recognized: (1) a postglacial negative delta 13C excursion (Npg interval); (2) a rising interval (Pr interval) of increasing positive delta 13C values; (3) a falling interval (Pf interval) characterized by decreasing positive delta 13C and culminating in near zero or negative values; and (4) an interval of moderately positive, relatively invariant delta 13C values (I interval) that extends up to the unconformity that contains the Proterozoic-Cambrian boundary. Each of these chemostratigraphic intervals can be recognized in widely separated correlative sections around the world. By comparing sediment accumulation rate in the radiometrically calibrated Namibian stratigraphy with sediment accumulation rates in correlative sections in Arctic Canada and Oman, a maximum age of 564 Ma is estimated for the end of the younger Varanger glaciation, 25 m.y. younger than previous estimates.

Carbon Isotopes↗
PubMed2005

Geochemical estimation of copper contamination in the healing mud from Makirina Bay, central Adriatic.

The coastal sediment from Makirina Bay in the central Adriatic represents an important source of healing mud (peloid) of high quality organoleptic properties that could in future be used for medical treatment. In this study, we estimated the contamination of the sediment with copper which can cause some undesirable health effects. Concentrations of Cu vary from 12 to 63 mg/kg in surface sediment and are higher in the central part of the Bay where the mud fraction prevails. Different normalizing methods were used, i.e. surface/background ratio, index of geoaccumulation, reference metal normalization, enrichment factor (EF) and grain size normalization, to compensate for the influence of the natural variability in sediment mineralogy and granulometry, and to assess whether the concentrations observed in surface sediment represent background or contaminated levels. Results show that Cu concentrations in the surface sediment are twice as high as local background values but in the same range as many clay materials used for medical treatment in Italy. The results also show that more detailed studies on Cu mobility are necessary prior to actual use of peloid in medical treatment.

Copper↗
PubMed2004

Heavy metal distribution and controlling factors within coastal plain sediments, Bells Creek catchment, southeast Queensland, Australia.

Bells Creek catchment in southeast Queensland (Australia) is a non-industrialised coastal plain limited to small settlements and agricultural land. A study was initiated to examine elevated metal concentrations and to assess horizontal and vertical distribution of those elements. Ninety-nine samples were analysed for Cr, V, Ni, Cu, Zn, Pb, As, Fe, Mn and Al. Total organic carbon, sulfur content and mineralogy of samples along with land-use practices across the catchment were used to identify processes which influence metal distribution. A comparison between metal concentration within the study area and mean heavy metal content of standard sandstone showed that except for Mn, all other metals showed elevated levels throughout the catchment. When metal concentrations were compared to parent bedrock, however, it was concluded that elevated levels are likely to be natural. A normalisation procedure was applied to the data set and this analysis validated that elevated trace metal concentrations in most samples are not due to artificial contamination. While surficial estuarine sediments were only enriched in V, soils were dominantly enriched in Cr, Zn and V. Overall, geochemistry and mineralogy of the samples show the effect of both natural and anthropogenic inputs to the catchment, however, natural processes are more dominant than anthropogenic inputs in concentrating metals.

Agriculture↗
PubMed2001

Standardized particle size for monitoring, inventory, and assessment of metals and other trace elements in sediments: <20 microm or <2 microm?

Despite the manifold factors that determine the composition of a river sediment (e.g., geology, soil type, rural or highly industrialized and densely populated, as well as forested areas, concentration of carbonates and organic matter), the linear regressions between the 9 metals determined in the fractions <2 microm and <20 microm have high coefficients (R2 after Pearson) for Cr and Cu (both 0.94), followed by Pb (0.90), Cd (0.82), Zn (0.81), Ni (0.76), and Mn (0.72). Low and very low coefficients are found for Hg (0.51) and Fe (0.22). In addition, the histograms of the metal ratios <2 microm:<20 microm (i.e. the slope of a linear regression) show that--with the exception of Cd (1.47)--all median ratios of the other metals fall within a narrow range (1.24-1.35). Both "fine" (<2 microm and <20 microm) fractions are able to fulfil the requirements for monitoring, inventory, and assessment of metals in sediments. Preference should be given to the rapid, simple, and economic <20 microm separation by sieving; this fraction corresponds fairly closely to the former suspended load of a riverine transport.

Fresh Water↗
PubMed2005

Influence of acid volatile sulfides and simultaneously extracted metals on the bioavailability and toxicity of a mixture of sediment-associated Cd, Ni, and Zn to polychaetes Neanthes arenaceodentata.

Laboratory microcosm experiments were conducted to investigate the influence of acid volatile sulfides (AVS) and simultaneously extracted metals (SEM) in sediments on the bioavailability and toxicity of Cd, Ni, and Zn in sediments to polychaete worms Neanthes arenaceodentata. Cohorts of juvenile N. arenaceodentata were exposed to sediments spiked with metal mixtures containing Cd, Ni, and Zn (0.5-15 micromol x g(-1) of total SEM) with Low- (approximately 1 micromol x g(-1)), Medium- (approximately 5 micromol x g(-1)), and High-AVS concentrations (approximately 10 micromol x g(-1)) for 20 days to determine mortality, growth rate, and metal bioaccumulation. Tissue Cd and Zn concentrations at the end of the exposure were significantly higher in sediments with the low-AVS concentration at a given SEM concentration due to the increased dissolved metal concentrations in overlying water (OW). However, tissue Ni concentrations were not related to dissolved Ni in the OW. AVS concentrations also influenced the toxicity of metals to the worms. Significant mortality was observed only at the highest SEM treatments at Low-AVS series. Most individuals survived at the highest SEM treatments at Medium- and High-AVS series. Similarly, the growth rates of worms were reduced in treatments having higher molar differences between SEM and AVS ([SEM-AVS]). Overall, the bioavailability and toxicity of metals in sediments was not well predicted by sediment metal concentrations only, but considering the influence of geochemical factors (AVS) on the metal bioavailability improved the prediction of toxicity. Also, the relationship between tissue metal concentration and toxicity was used to determine which contaminant was most responsible for the observed toxicity of the metal mixture.

Animals↗
PubMed1991

Lake Hoare, Antarctica: sedimentation through a thick perennial ice cover.

Lake Hoare in the Dry Valleys of Antarctica is covered with a perennial ice cover more than 3 m thick, yet there is a complex record of sedimentation and of growth of microbial mats on the lake bottom. Rough topography on the ice covering the lake surface traps sand that is transported by the wind. In late summer, vertical conduits form by melting and fracturing, making the ice permeable to both liquid water and gases. Cross-sections of the ice cover show that sand is able to penetrate into and apparently through it by descending through these conduits. This is the primary sedimentation mechanism in the lake. Sediment traps retrieved from the lake bottom indicate that rates of deposition can vary by large amounts over lateral scales as small as 1 m. This conclusion is supported by cores taken in a 3 x 3 grid with a spacing of 1.5 m. Despite the close spacing of the cores, the poor stratigraphic correlation that is observed indicates substantial lateral variability in sedimentation rate. Apparently, sand descends into the lake from discrete, highly localized sources in the ice that may in some cases deposit a large amount of sand into the lake in a very short time. In some locations on the lake bottom, distinctive sand mounds have been formed by this process. They are primary sedimentary structures and appear unique to the perennially ice-covered lacustrine environment. In some locations they are tens of centimetres high and gently rounded with stable slopes; in others they reach approximately 1 m in height and have a conical shape with slopes at angle of repose. A simple formation model suggests that these differences can be explained by local variations in water depth and sedimentation rate. Rapid colonization of fresh sand surfaces by microbial mats composed of cyanobacteria, eukaryotic algae, and heterotrophic bacteria produces a complex intercalation of organic and sandy layers that are a distinctive form of modern stromatolites.

Antarctic Regions↗
PubMed1991

Tourmaline mineralization in the Barberton greenstone belt, South Africa: early Archean metasomatism by evaporite-derived boron.

Tourmaline-rich rocks are common in the low-grade, interior portions of the Barberton greenstone belt of South Africa, where shallow-marine sediments and underlying altered basaltic and komatiitic lavas contain up to 50% tourmaline. The presence of tourmaline-bearing rip-up clasts, intraformational tourmaline pebbles and tourmaline-coated grains indicate that boron mineralization was a low-temperature, surficial process. The association of these lithologies with stromatolites, evaporites, and shallow-water sedimentary structures and the virtual absence of tourmaline in correlative deep-water facies rocks in the greenstone belt strengthens this model. Five tourmaline-bearing lithologic groups (basalts, komatiites, evaporite-bearing sediments, stromatolitic sediments, and quartz veins) are distinguished based on field, petrographic, and geochemical criteria. Individual tourmaline crystals within these lithologies show internal chemical and textural variations that reflect continued growth through intervals of change in bulk-rock and fluid composition accompanying one or more metasomatic events. Large single-crystal variations exist in Fe/Mg, Al/Fe, and alkali-site vacancies. A wide range in tourmaline composition exists in rocks altered from similar protoliths, but tourmalines in sediments and lavas have similar compositional variations. Boron-isotope analyses of the tourmalines suggest that the boron enrichment in these rocks has a major marine evaporitic component. Sediments with gypsum pseudomorphs and lavas altered at low temperatures by shallow-level brines have the highest delta 11B values (+2.2 to -1.9%); lower delta 11B values of late quartz veins (-3.7 to -5.7%) reflect intermediate temperature, hydrothermal remobilization of evaporitic boron. The delta 11B values of tourmaline-rich stromatolitic sediments (-9.8 and -10.5%) are consistent with two-stage boron enrichment, in which earlier marine evaporitic boron was hydrothermally remobilized and vented in shallow-marine or subaerial sites, mineralizing algal stromatolites. The stromatolite-forming algae preferentially may have lived near the sites of hydrothermal discharge in Archean times.

Boron↗
PubMed2003

Lossless compression of stromatolite images: a biogenicity index?

It has been underappreciated that inorganic processes can produce stromatolites (laminated macroscopic constructions commonly attreibuted to microbiological activity), thus calling into question the long-standing use of stromatolites as de facto evidence for ancient life. Using lossless compression on unmagnified reflectance red-green-blue (RGB) images of matched stromatolite-sediment matrix pairs as a complexity metric, the compressibility index (delta(c), the log ratio of the ratio of the compressibility of the matrix versus the target) of a putative abiotic test stromatolite is significantly less than the delta(c) of a putative biotic test stromatolite. There is a clear separation in delta(c) between the different stromatolites discernible at the outcrop scale. In terms of absolute compressibility, the sediment matrix between the stromatolite columns was low in both cases, the putative abiotic stromatolite was similar to the intracolumnar sediment, and the putative biotic stromatolite was much greater (again discernible at the outcrop scale). We propose tht this metric would be useful for evaluating the biogenicity of images obtained by the camera systems available on every Mars surface probe launched to date including Viking, Pathfinder, Beagle, and the two Mars Exploration Rovers.

Algorithms↗
PubMed2003

Anthropogenic 236U at Rocky Flats, Ashtabula river harbor, and Mersey estuary: three case studies by sector inductively coupled plasma mass spectrometry.

236U (t(1/2)=2.3 x 10(7) y) is formed as a result of thermal neutron capture by (235)U. In naturally occurring U ores, where a high neutron flux is present from spontaneous fission of (238)U, (236)U/(238)U atom ratios are approximately 10(-4) ppm. In the natural Earth's crust, unaffected by nuclear fallout, these ratios are expected to be on the order of 10(-8) ppm. Reactor-irradiated U, however, exhibits high (236)U/(238)U atom ratios approaching 10(4) ppm. As a result, the presence of very small quantities of reactor-irradiated U will significantly enhance the "background" (236)U/(238)U atom ratio. When sufficiently elevated (236)U/(238)U ratios are present, the determination of (236)U/(238)U by rapid inductively coupled plasma mass spectrometric (ICPMS) methods is attractive. We have used sector ICPMS at medium resolving power (R=3440) to measure (236)U/(238)U atom ratios with a determination limit of 0.2 ppm. The limiting factors in the measurement are the (235)U(1)H(+) isobar and background signal at m/z 236 arising from the (238)U(+) peak tail. Based upon the analysis of replicates and considerations of possible systematic errors, uncertainties of +/-5% are found for (236)U/(238)U atom ratios of 1-100 ppm. This procedure has been demonstrated in studies of anthropogenic (236)U in the environment at three locations: (a) offsite soils from the vicinity of the Rocky Flats Environmental Technology site (Golden, Colorado, USA); (b) sediments from the Ashtabula River (Ohio, USA); and (c) sediments from the Mersey estuary (Liverpool, UK). In each of these three locations, definite plumes of elevated (236)U/(238)U are identified and characterized. Maximum (236)U/(238)U atom ratios observed in RFETS-vicinity soils, the Ashtabula River, and the Mersey Estuary are 2.8, 140, and 4.4 ppm, respectively.

Colorado↗
PubMed1990

Aerobic respiration in the Archaean?

The Earth's atmosphere during the Archaean era (3,800-2,500 Myr ago) is generally thought to have been anoxic, with the partial pressure of atmospheric oxygen about 10(-12) times the present value. In the absence of aerobic consumption of oxygen produced by photosynthesis in the ocean, the major sink for this oxygen would have been oxidation of dissolved Fe(II). Atmospheric oxygen would also be removed by the oxidation of biogenic methane. But even very low estimates of global primary productivity, obtained from the amounts of organic carbon preserved in Archaean rocks, seem to require the sedimentation of an unrealistically large amount of iron and the oxidation of too much methane if global anoxia was to be maintained. I therefore suggest that aerobic respiration must have developed early in the Archaean to prevent a build-up of atmospheric oxygen before the Proterozoic. An atmosphere that contained a low (0.2-0.4%) but stable proportion of oxygen is required.

Aerobiosis↗
PubMed2003

Applying foraminiferal stratigraphy as a biomarker for heavy metal contamination and mining impact in a fiord in West Greenland.

Sulphidic mine waste disposed in marine environments constitutes an environmental risk to aquatic life due to potential uptake and accumulation of heavy metals in biota. Fiord sediments near the former Black Angel Mine in West Greenland are contaminated by lead and zinc as a result of submarine tailings disposal in 1973-1990. In 1999 cores were taken up to 10 km away from the disposal area. Analyses include heavy metals, radiochemical dating (210Pb) and high-resolution foraminiferal stratigraphy. The mining operation resulted in significant changes in the assemblage composition. In addition, up to 20% of the Melonis barleeanus population found in sediment deposited during nearby tailings disposal was deformed compared to a natural background of less than 5%. Throughout cores representing the last 100 years of sedimentation, the total numbers and frequency of morphological abnormalities among M. barleeanus revealed some correlation with heavy metals concentrations (up to r2 = 79%). We conclude that abnormalities among foraminifera may represent a useful biomarker for evaluating trends in the biological impact resulting of submarine tailings disposal as well as long-term environmental impact and subsequent recovery.

Animals↗