Fine particulate organic matter (FPOM) transport and processing in littoral interstices – use of fluorescent markers

A fluorescent labelling method is presented as a new tool for the investigation of organic particle transport and biogenic carbon cycling processes in sandy littoral interstices at Lake Tegel, Berlin, Germany. Passive particle transport through the pore system was studied by in situ exposition of 2.4 μm monodisperse polymeric resin microparticles stained with 7-amino-4-methylcoumarin (AMC). Uptake of fluorescein-5-isothiocyanate (FITC)-labelled Chlorella vulgaris and fine particulate organic matter (FPOM) by the interstitial fauna was investigated in laboratory and field experiments. The major portion (>85%) of the FITC-labelled particles added to sediment cores was recovered from the topmost centimetre of sediment during the study period of 14 days. Uptake of FITC-labelled FPOM was observed in several benthic groups, e.g. chironomids, microcrustaceans, oligochaetes and tardigrads, whereas C. vulgaris was ingested by oligochaetes only. There is evidence to suggest that both are suitable materials for investigating the fragmentation and ingestion of organic material by herbivorous and detritivorous fauna. Field experiments with inert microparticles and FITC-labelled FPOM (<1 mm) prepared from dried alder leaves were carried out in plexiglass tubes as in situ whole core technique. Within the investigation period of two weeks, the transport of FPOM was restricted to the topmost 2–3 cm of sediment in conjunction with a distinct fragmentation to finer size classes with respect to increasing sediment depth. Vertical FPOM transport was hindered by a high interstitial concentration of natural POM and an intensive settlement of the interstices by algae (mainly epispammic algae, 65–96% of algae cell number) and extra-cellular polymeric substances (EPS), which formed a dense three-dimensional structure.     

Deriving hillslope sediment budgets in wildfire-affected forests using fallout radionuclide tracers

Information on post-fire sediment and nutrient redistribution is required to underpin post-fire catchment management decisions. Fallout radionuclide budgets (²¹⁰Pb_xs, ¹³⁷Cs and ⁷Be) were derived to quantify soil redistribution and sediment yield in forested terrain following a moderately severe wildfire in a small (89 ha) water supply catchment in SE Australia. Application of these techniques in burnt terrain requires careful consideration of the partitioning of radionuclides between organic and mineral soil components. Beryllium-7 and ²¹⁰Pb_xs were shown to be closely associated with ash, litter and soil organic matter whereas ¹³⁷Cs was more closely associated with subsurface coarse mineral soil. Comparison of the three tracer budgets indicated that the dominant sediment source areas were ridgetops and steep valley sideslopes, from which burnt surface material was conveyed to the stream network via pre-existing gullies. Erosion was predominantly driven by sheetwash, enhanced by soil water repellency, and modified by bioturbation which both supplies subsurface sediment and provides sinks for erosive overland flow. Footslope and riparian zones were not important sediment source areas. The estimated event-based (wildfire and subsequent rainfall) sediment yield is 58 ± 25 t km^− 2, based on fallout ⁷Be measurements. The upper estimate of total particulate phosphorus yield (0.70 kg ha^− 1) is more than 10 times that at equivalent unburnt sites. This illustrates that, soon after fire, burnt eucalypt forest can produce nutrient loads similar to those of agricultural catchments. The tracer budgets indicate that wildfire is an important control on sediment and phosphorus inputs to the stream network over the decadal timeframe and the pulsed nature of this release is an important concern for water quality management.     

The mass of the Andromeda galaxy

This paper argues that the Milky Way galaxy is probably the largest member of the Local Group. The evidence comes from estimates of the total mass of the Andromeda galaxy (M31) derived from the three-dimensional positions and radial velocities of its satellite galaxies, as well as the projected positions and radial velocities of its distant globular clusters and planetary nebulae. The available data set comprises 10 satellite galaxies, 17 distant globular clusters and nine halo planetary nebulae with radial velocities. We find that the halo of Andromeda has a mass of together with a scalelength of 90 kpc and a predominantly isotropic velocity distribution. For comparison, our earlier estimate for the Milky Way halo is Although the error bars are admittedly large, this suggests that the total mass of M31 is probably less than that of the Milky Way . We verify the robustness of our results to changes in the modelling assumptions and to errors caused by the small size and incompleteness of the data set.
Our surprising claim can be checked in several ways in the near future. The numbers of satellite galaxies, planetary nebulae and globular clusters with radial velocities can be increased by ground-based spectroscopy, while the proper motions of the companion galaxies and the unresolved cores of the globular clusters can be measured using the astrometric satellites Space Interferometry Mission ( SIM ) and Global Astrometric Interferometer for Astrophysics ( GAIA ). Using 100 globular clusters at projected radii 20 R 50 kpc with both radial velocities and proper motions, it will be possible to estimate the mass within 50 kpc to an accuracy of 20 per cent. Measuring the proper motions of the companion galaxies with SIM and GAIA will reduce the uncertainty in the total mass caused by the small size of the data set to 22 per cent.     

The peterson limestone — early cretaceous lacustrine carbonate deposition in western wyoming and southeastern idaho

The lacustrine Peterson Limestone of western Wyoming and southeastern Idaho comprises six lithofacies throughout its 20,000 km² aerial extent. These are: (1) calcareous sandstone and shale, (2) red nodular limestone, (3) pink sandy micrite, (4) biomicrite, (5) graded silty micrite, and (6) limestone conglomerate. The first two represent floodplain deposition and paleosols, whereas the remaining are shallow nearshore and deeper lacustrine sediments.This sequence was developed in a large fresh, hardwater lake surrounded by fluvial systems and associated flood plains in a warm temperate climate. Well-oxidized sandy terrigenous rocks, together with calcareous paleosol nodules, indicate that flood-plain deposition both preceded and was concurrent with lacustrine carbonate deposition. Micrite and biomicrite formed in deeper parts of the basin while sandy and silty carbonate accumulated in shallower lake-margin areas. Less-calcareous shale units which are interbedded with deeper-water carbonate were deposited either during rapid basin subsidence and deepening of the lake center or during periods of slower carbonate precipitation. Turbidity currents and subaqueous debris flows generated along steeper lake margins, resulted in the deposition of rhythmic layers of graded silty micrite and diamictic limestone conglomerate in the deepest part of the basin. The carbonate-rich sediments comprising these two lithofacies were originally deposited on shallow lake-margin benches and subsequently were transported downslope toward the lake center.Comparison with other carbonate-precipitating lacustrine systems indicates that this lake was not like modern playas. Although no known modern lacustrine system is precisely like Lake Peterson, the flora, fauna, composition, and distribution of facies within modern temperate-region lakes most closely resemble those of the Peterson Limestone.     

The nature of crystalline silica from the TAG submarine hydrothermal mound, 26°N Mid Atlantic Ridge

Silica occurs in abundance in a variety of hydrothermal samples from the Trans-Atlantic Geotraverse (TAG) hydrothermal mound, 26°N Mid-Atlantic Ridge. The water content, trace element chemistry, and mineralogy of crystalline silica from 15 different samples have been examined by vibrational spectroscopy and probe microanalysis. The samples are from: shallow subsurface ferric iron oxyhydroxide silica deposits (n=4), a fragment of an active white smoker chimney (n=1), anhydrite bearing hydrothermal breccias (n=2), pyrite silica breccias (n=3), and silicified wall rock breccias (n=5). Length-fast chalcedony occurs in association with variable quantities of ferric iron oxyhydroxides in hydrothermal breccias from the mound flanks, within shallower subsurface chert samples, and within white smoker chimney walls. Samples from the anhydrite zone contain textures which are suggestive of an origin involving replacement of anhydrite. Samples taken from TAG 1 and 5 from below the anhydrite zone contain no chalcedony. Instead they contain subhedral quartz crystals which show oscillatory zoning in aluminium. Two types of crystalline silica namely, type A and type B quartz, are defined on the basis of the infrared spectra in the OH region from 3200 cm⁻¹ to 3600 cm⁻¹. The type A quartz occurs beneath the anhydrite zone at TAG 1 and 5. We propose a model that relates specific varieties of crystalline silica to different thermal and chemical environments within the mound interior. Length-fast chalcedony occurs in an outer low temperature envelope across the top and sides of the mound. The common association between length-fast chalcedony and ferric iron oxyhydroxides suggests that chalcedony crystallization is favoured where catalysis by ferric iron can occur. The apparent suppression of fibrous silica at the expense of single quartz crystals with increasing depth is attributed to differing growth rates and degrees of supersaturation of silica-bearing solutions with increasing temperature within the mound. The transition from type A to type B single crystal growth is interpreted to occur at temperatures approaching ˜360 °C due to decreasing solubility of aluminium in quartz, so that aluminium is rendered unavailable for type A valence compensation. Received: 10 September 1998 / Accepted: 6 July 1999     

Disseminated ‘jigsaw piece’ dolomite in Upper Jurassic shelf sandstones,Central North Sea: an example of cement growth during bioturbation?

Unusual textural and chemical characteristics of disseminated dolomite in Upper Jurassic shelf sediments of the North Sea have provided the basis for a proposed new interpretation of early diagenetic dolomite authigenesis in highly bioturbated marine sandstones. The dolomite is present throughout the Franklin Sandstone Formation of the Franklin and Elgin Fields as discrete, non‐ferroan, generally unzoned, subhedral to highly anhedral ‘jigsaw piece’ crystals. These are of a similar size to the detrital silicate grains and typically account for ≈5% of the rock volume. The dolomite crystals are never seen to form polycrystalline aggregates or concretions, or ever to envelop the adjacent silicate grains. They are uniformly dispersed throughout the sandstones, irrespective of detrital grain size or clay content. Dolomite authigenesis predated all the other significant diagenetic events visible in thin section. The dolomite is overgrown by late diagenetic ankerite, and bulk samples display stable isotope compositions that lie on a mixing trend between these components. Extrapolation of this trend suggests that the dolomite has near‐marine δ¹⁸O values and low, positive δ¹³C values. The unusual textural and chemical characteristics of this dolomite can all be reconciled if it formed in the near‐surface zone of active bioturbation. Sea water provided a plentiful reservoir of Mg and a pore fluid of regionally consistent δ¹⁸O. Labile bioclastic debris (e.g. aragonite, Mg‐calcite) supplied isotopically positive carbon to the pore fluids during shallow‐burial dissolution. Such dissolution took place in response to the ambient ‘calcite sea’ conditions, but may have been catalysed by organic matter oxidation reactions. Bioturbation not only ensured that the dissolving carbonate was dispersed throughout the sandstones, but also prohibited coalescence of the dolomite crystals and consequent cementation of the grain framework. Continued exchange of Mg²⁺ and Ca²⁺ with the sea‐water reservoir maintained a sufficient Mg/Ca ratio for dolomite (rather than calcite) to form. Irregular crystal shapes resulted from dissolution, of both the dolomite and the enclosed fine calcitic shell debris, before ankerite precipitation during deep‐burial diagenesis.     

An Al-spinel ultramafic-mafic inclusion suite and high pressure megacrysts in an analcimite and their bearing on basaltic magma fractionation at elevated pressures

An analcimite sill, which intrudes Carboniferous sedimentary rocks northwest of the township of Barraba in northeastern New South Wales, is exceedingly rich in ultramafic and mafic inclusions and also contains a varied megacryst assemblage. The majority of inclusions belong to an ultramafic-mafic granulite suite whose members generally contain a Cr-poor green spinel. Layering is preserved in many inclusions and their textures are appropriate to those arising from recrystallization at subsolidus temperatures. Ultramafic granulites of the Al-spinel suite are mainly pyroxenites, with rarer lherzolites, and mafic granulites usually consist of the assemblage plagioclasea-luminous pyroxenes-spinel. Ca-rich tschermakitic clinopyroxenes and coexisting aluminous Ca-poor orthopyroxenes define a trend of moderate iron enrichment. Spinels also display significant Fe²⁺ → Mg substitution. Plagioclase in some plagioclase-bearing pyroxenites and mafic granulites contains numerous rod-like inclusions of spinel, compositionally similar to the discrete spinels unassociated with plagioclase. The formation of spinel in plagioclase is believed to have resulted largely from the migration of (Mg, Fe²⁺) to Al-rich nucleation sites in the feldspar. Other inclusion types include Cr-spinel lherzolites —more Fe-rich than Cr-diopside lherzolite inclusions in alkaline volcanics — and rare wehrlite heteradcumulates, probably cognate with the host analcimite. The megacryst assemblage is dominated by anorthoclase megacrysts, which are accompanied, in order of decreasing abundance, by megacrysts of tschermakitic clinopyroxene, titanbiotite, kaersutite, and aluminous titanomagnetite. The Al-spinel mafic granulites have low Ti, K and P contents and their petrochemical affinities are high-alumina mafic alkaline to transitional. They compare closely in major and minor element chemistry with some ocean ridge basalts. The Al-spinel ultramafic-mafic inclusions suite is interpreted as the remnants of a layered ultramafic-mafic “pluton ” which initially crystallized at pressures in the vicinity of 10 kb and subsequently re-equilibrated at subsolidus temperatures (ca 950° C) and comparable pressures. The parent magma was K-poor, ol-normative subalkaline and its fractionation at moderate pressures, controlled mainly by olivine and subcalcic clinopyroxene, resulted in decreases in the derivative liquids in their saturation levels and ol contents, and increases in Al and Ca. These trends are reflected in the compositions of the mafic granulites. The pressure regime of megacryst formation apparently was greater than 10–12 kb i.e. the megacrysts precipitated before acquisition of xenoliths of the Al-spinel granulite suite by the analcimite host. Anorthoclase fractionation produced only limited compositional changes in the original alkali basaltic melt.     

Environmental effects of river sand mining: a case from the river catchments of Vembanad lake,Southwest coast of India

Rivers in the southwest coast of India are under immense pressure due to various kinds of human activities among which indiscriminate extraction of construction grade sand is the most disastrous one. The situation is rather alarming in the rivers draining the Vembanad lake catchments as the area hosts one of the fast developing urban-cum-industrial centre, the Kochi city, otherwise called the Queen of Arabian Sea. The Vembanad lake catchments are drained by seven rivers whose length varies between 78 and 244 km and catchment area between 847 and 5,398 km². On an average, 11.73 million ty⁻¹ of sand and gravel are being extracted from the active channels and 0.414 million ty⁻¹ of sand from the river floodplains. The quantity of instream mining is about 40 times the higher than the sand input estimated in the gauging stations. As a result of indiscriminate sand mining, the riverbed in the storage zone is getting lowered at a rate of 7–15 cm y⁻¹ over the past two decades. This, in turn, imposes severe damages to the physical and biological environments of these river systems. The present paper deals with the environmental effects of indiscriminate sand mining from the small catchment rivers in the southwest coast of India, taking the case of the rivers draining the Vembanad lake catchments as an example.     

An analcime mugearite-megacryst association from north-eastern New South Wales: implications for high-pressure amphibole-dominated fractionation of alkaline magmas

An analcime-rich mugearite near Spring Mount in north-eastern New South Wales contains dominant kaersutite, lesser anorthoclase and rare Ti-rich mica megacrysts, and also rare Group I peridotite xenoliths and granitoid inclusions. Mineralogical, experimental and Sr and Nd isotopic data are interpreted to indicate that the megacrysts are cognate with their host and that megacryst precipitation occurred at pressures in the vicinity of 1 GPa. Isotopic and other data indicate minimal crystal contamination of the melt. The generation of this evolved lava (100 Mg/(Mg+Fe²⁺), M55; differentiation index DI52–56) by high-pressure amphiboledominated fractionation of a mantle-derived hydrous alkali basaltic parent (M70) is inconsistent with observed megacryst abundances (<3%) and absence of Group II cumulates, and with the magnitude of the crystal extracts (45% crystals) indicated by crystal fractionation models. These data suggest the mugearite is not a high-pressure differentiate of a hypothetical primary parental magma (M70). Alternatively, its composition might approximate that of a primary magma derived from a relatively Fe-rich amphibole lherzolite mantle source.     

Reviews

F. L. Stillwell Anniversary Volume. Australian Institute of Mining and Metallurgy, Melbourne, 302 pages, many plates and figures. 1958.

Our Mineral Resources, by Charles M. Riley; x + 338 pages; 102 figures; John Wiley and Sons, Inc., New York and London. $6.95.

Researches in Geochemistry, edited by P. H. Abelson; John Wiley and Sons Inc., New York, 1959. $11.00.

Basic Geology for Science and Engineering, by Edward C. Dapples; vii + 609 pages; 231 figures. John Wiley and Sons Inc., New York, 1959. $9.50.

Historical Geology, by Carl O. Dunbar; xi + 500 pages; 406 figures. Second Edition, publication date August, 1960; John Wiley and Sons Inc., New York. $7.95.

Time, Life and Man, by R. A. Stirton; xi + 558 pages; 291 figures. John Wiley and Sons Inc., New York, 1958.

Vector Space, by Martin J. Buerger; xiv + 347 pages; numerous line drawings; John Wiley and Sons Inc., New York and London. $12.00.

Geology of the Country Around Polonnaruwa, by Piyadasa W. Vtkanage. 1959. Memoir No. 1, Department of Mineralogy, Geological Survey of Ceylon; ix + 75 pages; 11 figures; 12 plates.