Mikrofossilien in Süsswassersedimenten

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Trace metal distribution in Baltic Sea ferromanganese concretions: inferences on accretion rates

The usually high concentrations of Zn, Pb, Cd, and Cu in the most recently accreted portions of ferromanganese nodules from the western Baltic Sea are thought to reflect increased metal input due to anthropogenic mobilization. If so, the point of increase represents a time horizon within the structure of the nodule. Similar trace metal distributions of radiometrically dated sediments from the same area suggest that the ferromanganese nodules have grown in thickness between 0.02 and 0.16 mm yr^?1. From this growth rate anthropogenic Zn flux to the nodule surface was calculated to be 80 mg m^?2 yr^?1.     

Die physikalische und chemische Erforschung der Donau

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Some geochemical aspects of sedimentary rocks in proximity of coals, sydney coalfield (upper carboniferous), cape breton island, nova scotia, canada

Channel samples of roof and seat rocks (lutites, siltstone)) of 10 successional coals, in addition to red mudstone and calcareous siltstones, have been collected from the Sydney Coalfield, Nova Scotia. The channel samples are confined to within 150 cm above the top of coals, and to within 20 cm below the bottom of coals. Whole-rock and trace-elemental analyses are reported: wt. % of oxides of Si, Al, total Fe, Ca, Mg, Na, K, T1, Mn; and ppm's for Cu, Ni, Pb, Zn, Cr, Co, Ga, V, As, U, and Th, respectively. Th/U ratios, organic carbon and carbonate carbon of selected roof rock samples are also reported.The comparatively small stratugraphic mean variations of Na₂/K₂O and Na₂O/Al₂O₃ are open to interpretation but may indicate either a common sedimentary source, or a similar diagenetic history during basin development. Assumed is that the oxide ratios originated from detrital feldspars and clays. The probability model for uranium is Pearson's Type VII curve. The relationship between uranium (thorium) and (assumed) organic calcite in selected calcareous siltstones is examined. Stratigraphic variation of the geochemistry is assumed to be cycle-controlled, excepting probably As, V, and Cu,which under the stated conditions are amenable to mathematical modeling (of sedimentary cycles).     

Authigenic gypsum found in gas hydrate-associated sediments from Hydrate Ridge, the eastern North Pacific

Hydrate Ridge is located at the second accretion-ary ridge along the Cascadia margin of Oregon in the eastern North Pacific (fig. 1). The Bottom Simulating Reflector (BSR) underlies the entire Hydrate Ridge[1]. The Ocean Drilling Program (ODP) in 1992 at Site 892 and the TECFLUX99 and 2000 showed that the gas hydrate occurs just beneath the thin sediment- covered surface and at the horizon of around 64 meter below seafloor (mbsf) on Hydrate Ridge[25]. The col-lision of the Juan de …     

Created versus natural coastal islands: Atlantic waterbird populations, habitat choices, and management implications

Nesting colonial waterbirds along the Atlantic Coast of the United States face a number of landscape-level threats including human disturbance, mammalian predator expansion, and habitat alteration. There have been changes from 1977 to the mid-1990s in use of nesting habitats and populations of a number of seabird species of concern in the region, including black skimmersRynchops niger Linnaeaus, common ternsSterna hirundo Linnaeaus, gull-billed ternsSterna nilotica Linnaeaus, least ternsSterna antillarum Lesson, royal ternsSterna maxima Boddaert, and sandwich ternsSterna sandvicensis Cabot. These species form colonies primarily on the following habitat types: large, sandy barrier or shoal islands, natural estuarine or bay islands (mostly marsh) man-made islands of dredged deposition materials (from navigation channels), and the mainland. Significant changes in the use of the dredged material islands have occurred for these species in New Jersey and North Carolina, but not in Virginia. Population declines and changes in bird habitat use appear to be at least partially associated with the conditions and management of the existing dredged material islands, coastal policy changes associated with creating new dredged material islands, and competing demands for sand for beach augmentation by coastal communities. As these and other coastal habitats become less suitable for colonial waterbirds, other man-made sites, such as, bridges and buildings have become increasingly more important. In regions with intense recreational demands, coastal wildlife managers need to take a more aggressive role in managing natural and man-made habitats areas and as stakeholders in the decision-making process involving dredged materials and beach sand allocation.     

Groundwater chemistry of Al under Dutch sandy soils: Effects of land use and depth

Aluminium has received great attention in the second half of the 20th century, mainly in the context of the acid rain problem mostly in forest soils. In this research the effect of land use and depth of the groundwater on Al, pH and DOC concentration in groundwater under Dutch sandy soils has been studied. Both pH and DOC concentration play a major role in the speciation of Al in solution. Furthermore, the equilibrium with mineral phases like gibbsite, amorphous Al(OH)₃ and imogolite, has been considered. Agricultural and natural land use were expected to have different effects on the pH and DOC concentration, which in turn could influence the total Al concentration and the speciation of Al in groundwater at different depths (phreatic, shallow and deep). An extensive dataset (n = 2181) from the national and some provincial monitoring networks on soil and groundwater quality was used. Land use type and groundwater depth did influence the pH, and Al and DOC concentrations in groundwater samples. The Al concentration ranged from <0.4 μmol L⁻¹ at pH > 7 to 1941 μmol L⁻¹ at pH < 4; highest Al concentrations were found for natural-phreatic groundwater. The DOC concentration decreased and the median pH increased with depth of the groundwater. Natural-phreatic groundwater showed lower pH than the agricultural-phreatic groundwater. Highest DOC concentrations were found for the agricultural-phreatic groundwater, induced by the application of organic fertilizers. Besides inorganic complexation, the NICA-Donnan model was used to calculate Al³⁺ concentrations for complexation with DOC. Below pH 4.5 groundwater samples were mainly in disequilibrium with a mineral phase. This disequilibrium is considered to be the result of kinetic constraints or equilibrium with organic matter. Log K values were derived by linear regression and were close to theoretical values for Al(OH)₃ minerals (e.g. gibbsite or amorphous Al(OH)₃), except for natural-phreatic groundwater for which lower log K values were found. Complexation of Al with DOC is shown to be an important factor for the Al concentrations, especially at high DOC concentrations as was found for agricultural-phreatic groundwater.     

Toward a definition of a mineral sample in geology

Summary Any rock may be regarded as an aggregate of mineral species frequency distributions, thus opening up a new method of analyzing the problems of the nature of these discrete distributions.Based on theorems in mathematical probability, a subrock sample is defined as a probability sample under the conditions that every mineral species' distribution function in this subrock converges probabilistically to one and the same distributions the nature of which is immaterial at this point.For obvious reasons, the situation is excluded if the sample size approaches infinity, i.e., Chebyshev's theorem (Chebyshev, 1867).