Yellow Clay Research Articles

Field experiments on mitigation of harmful algal blooms using a Sophorolipid—Yellow clay mixture and effects on marine plankton

This study examined a new method of mitigating harmful algal blooms (HABs) by combining biosurfactant sophorolipid and yellow clay. To investigate the effects and practicability of this HAB mitigation method, field experiments were carried out during a Cochlodinium bloom near Miruk Island, South Korea, in August 2002. Field experiments examined the effects of sophorolipid and yellow clay on Cochlodinium bloom mitigation and on marine plankton such as bacteriaplankton, heterotrophic protists, and zooplankton. A mixture of 5 mg l −1 sophorolipid and 1 g l −1 yellow clay was sprayed directly on the sea surface and its effect was compared with that of 10 g l −1 of yellow clay applied under similar conditions. The sophorolipid–yellow clay mixture more efficiently mitigated the Cochlodinium bloom (95% removal efficiency after 30 min) than yellow clay alone (79% after 30 min). Further, no variation in bacterial abundance occurred 30 min after spraying the sophorolipid–yellow clay mixture. After 30 min, heterotrophic protist abundance at the surface decreased 21 and 41%, respectively, following the sophorolipid–yellow clay mixture and yellow clay treatments. Zooplankton decreased by 38% 15 min after spraying the mixture and 67% 30 min after spraying the yellow clay. These results indicate that the mixture of sophorolipid and yellow clay had a less adverse effect on bacteriaplankton, heterotrophic protists, and zooplankton than the yellow clay, suggesting that the sophorolipid–yellow clay mixture can mitigate HABs efficiently with fewer negative effects on the pelagic ecosystem.

육계의 사료내 황토 첨가가 계육의 관능적 특성에 미치는 영향

육계 사료내 황토의 첨가가 계육의 조리시 관능적 특성에 미치는 영향을 조사한 결과는 다음과 같다. 공시 동물은 Ross Broiler 216수로 6처리 6반복 반복당 6수씩 사양 시험을 실시하였다. 처리구는 1) 대조구, 2) 황토 0.5% 첨가구, 3) 황토 1.0% 첨가구, 4) 황토 2.0% 첨가구, 5) 황토 4.0% 첨가구, 6) 황토 8.0% 첨가구로 총 6처리로 나누어 급여한 후 관능적 특성을 조사하였다. 황토 첨가구는 대조구에 비하여 조리 전에는 L값은 유의적인 차이가 나타나지 않았으나, 조리 후에는 유의적으로 증가하였고(P<0.05), 조리 전보다 조리 후에 L값이 더 높았다. a값은 조리 전의 경우 대조구에 비하여 황토 첨가구는 더 낮게 나타난 반면, 조리 후에는 대조구보다 황토 첨가구가 더 높게 나타났다. b값은 조리 전의 경우 대조구에 비하여 4.0 및 8.0% 첨가구에서 높게 나타났고, 조리 전보다 조리 후 b값은 높게 나타났다. 경도, 점착성 및 씹힘성은 조리 전과 후 모두 대조구에 비하여 황토 첨가량이 증가함에 따라 낮아졌다(P<0.05). 조리 후 육수의 탁도는 사료내 황토 첨가량이 증가할수록 높게 나타났다(P<0.05). 관능 평가에서 육질과 육수의 색, 향미, 맛, 질감 등은 대조구보다 황토 첨가구의 기호도가 높았으며(P<0.05), 전체적인 선호도는 4.0% 황토첨가구가 가장 높게 나타났다(P<0.05). 따라서 육계의 사료 황토를 첨가하여 생산한 계육은 관능 평가 결과 기호성을 향상시킬 수 있는 방법으로 사료된다. This experiment was conducted to research the effects of Yellow Clay(YC) on the sensory evaluation of cooked meat in broiler chicks. A total of 216 one day old broiler chicks were divided into 6 groups at random. The six groups are consisted of one control group, to which no YC was added, and 5 groups to which an amount of YC was differently added. Diets contained 0.5, 1.0, 2.0, 4.0 and 8.0% of YC and fed to the 5 group broilers for 6 weeks. The lightness of meat in the broilers treated with YC was significantly higher than that of the control group in after-cooking(P<0.05). Besides, the lightness of meat was higher after-cooking than before-cooking. The properties of hardness, gumminess and chewiness were significantly lowered in the groups treated with Yellow Clay, as the amount of Yellow Clay increased at before-cooking and after-cooking(P<0.05). The turbidity of stock was higher in the groups treated with Yellow Clay as the percentage level of Yellow Clay increased, compared with the control group(P<0.05). The acceptability of color, flavor, and texture of meat and stock was higher in the groups treated with Yellow Clay, when compared with that of the control group(P<0.05). In total, the group treated with the 4 percentage of Yellow Clay was the highest in the overall preference(P<0.05).

Chicxulub impact predates K–T boundary: New evidence from Brazos, Texas

Multidisciplinary studies, including stratigraphy, sedimentology, mineralogy and geochemistry, of the new core Mullinax-1 and outcrops along the Brazos River and Cottonmouth Creek, Falls County, Texas, reveal the complex history of the Chicxulub impact, the event deposit and the K–T boundary event. The K–T boundary, as identified by the negative δ 13C shift, first occurrence of Danian planktic foraminifera and palynomorphs occurs 80 cm above the event deposit in core Mullinax-1. The underlying 80 cm interval was deposited in a shallow low oxygen environment during the latest Maastrichtian, as indicated by high stress microfossil assemblages, small shells and burrows infilled with framboidal pyrite. The underlying event deposit, commonly interpreted as K–T impact tsunami, consists of a basal conglomerate with clasts containing Chicxulub impact spherules, repeated upward fining units of spherule-rich sands, followed by hummocky cross-bedded and laminated sands, which are burrowed by Thalassinoides, Planolites and Ophiomorpha and truncated by erosion. This suggests a series of temporally separated storm events with re-colonization of the ocean floor by invertebrates between storms, rather than a series of waning tsunami-generated waves. The lithified clasts with impact spherules at the base of the event deposit provide strong evidence that the Chicxulub impact ejecta layer predates the event deposit, but was eroded and re-deposited during the latest Maastrichtian sea level lowstand. The original Chicxulub ejecta layer was discovered in a 3 cm thick yellow clay layer interbedded in undisturbed late Maastrichtian clay- and mudstones 40 cm below the base of the event deposit and near the base of planktic foraminiferal zone CF1, which spans the last 300 kyr of the Maastrichtian. The yellow clay consists of cheto smectite derived from alteration of impact glass, as indicated by rare altered glass spherules with similar chemical compositions as reworked spherules from the event deposit and Chicxulub impact spherules from NE Mexico and Haiti. The Brazos sections thus provide strong evidence that the Chicxulub impact predates the K–T boundary by about 300 kyr, consistent with earlier observations in NE Mexico and the Chicxulub crater core Yaxcopoil-1.

Weathering of Valle Ricca stiff and jointed clay

The study proposes a weathering model of Pliocene–Pleistocene stiff and jointed blue-grey clay transforming into yellow clay. Physical, mineralogical, chemical and textural changes, as well as the weathering profile were investigated in a quarry of central Italy. Based on geological records and inferences, these changes are likely to have occurred within a time-span of about 50,000 years BP, upon overburden stress unloading and in a stress regime that is locally controlled by suction. Weathering propagated into the clay at a rate of about 0.3 mm/year and was enhanced by the enlargement of the pre-existing tectonic discontinuities and by the formation of new joints. A mass loss of about 22–25 wt.% was calculated. Considering Fe and P as immobile elements, the individual oxides contribute to mass loss in the following order: SiO 2 > CaO = CO 2 > Al 2O 3 > MgO > K 2O > S > Na 2O > TiO 2 > MnO. The Fe 2O 3 / (Fe 2O 3 + FeO) ratio varies from 9–29% in the blue-grey clay to 75–82% in the yellow one. Oxidation and/or dissolution of 7 Å-Fe 2+-bearing clay minerals, mica-like minerals and calcite and parallel increase of smectite and Fe-hydroxides play a critical role in the chemical changes and explain the higher plasticity of the yellow clay with respect to the blue-grey one. The role of water during the weathering process was inferred to occur in cyclical steps: 1) seepage of meteoric water; 2) dissemination of highly oxidizing meteoric water; 3) triggering of oxidation and dissolution of minerals; 4) water evaporation; 5) partial migration of the elements contained in the aqueous solution and consequent deposition of minerals in the joints.

Host color preferences and short‐range searching behavior of the egg parasitoid Trichogramma ostriniae

AbstractThe color of lepidopteran eggs often varies by species or egg condition, and parasitoids that attack lepidopteran eggs could therefore potentially use color to obtain information about host identity or quality. The objective of our study was to determine whether females of the egg parasitoid Trichogramma ostriniae Pang &amp; Chen (Hymenoptera: Trichogrammatidae) showed differential responses to egg color when searching for hosts over short distances and when evaluating the suitability of encountered eggs. We examined the wasps’ host‐selection behavior in a Petri dish arena using white, yellow, green, and black clay beads as egg models presented against a green background (to mimic leaf color). In no‐choice tests, bead color had a significant effect on the proportion of tested wasps that accepted a bead for further examination, on the time it took wasps to find and begin examining a bead, and on the time that wasps spent examining the beads. However, bead color had only a marginally significant effect on the proportion of wasps attempting to drill into a bead with their ovipositors, and no significant effect on the amount of time they spent drilling. The wasps also showed significant color preferences when given a choice between two adjacent beads of different colors. The results of the no‐choice and choice trials taken together indicated a color preference ranking of yellow &gt; white &gt; green &gt; black. The wasps’ higher preference for the yellow and white egg models generally corresponds to the white or yellowish‐white egg color of T. ostriniae's target host, the European corn borer moth, Ostrinia nubilalis Hübner (Lepidoptera: Crambidae). The wasps’ strong rejection of black egg models is likely to be an adaptive response that reflects the fact that eggs that are wholly or partially black are often unsuitable for parasitization due to advanced caterpillar development, damage to the egg, or previous parasitization.

Ability of Certain Clays in Decolarization of Lubricant Oil

Various types of clays (namely, yellow bentonite, brown bentonite, and Kaolin) of Iraqi Kurdistan&#x0D; have been used for decolorizing dark oils and compared with activated China clay and Iranian clay called&#x0D; (Rose); which are largely used for the industriai processing of mineral oils. Chemical analysis has been&#x0D; made for all clay saniples for determination of their chemical compositions then different amounts&#x0D; (percentage) ofeach clay (3-11%iviv) have been used lor the decolorizing process ofthe lubricant oil, that&#x0D; manufactured at Sulaimani city at tixed temperature and particle size. Later, studies of different&#x0D; temperatures (150,200.250,300"C) at fixed amount of clay have been carried out to show the temperature&#x0D; effect on adsorption process. The decolorizing efficiency' of clays was found to be in the following order;&#x0D; China clay, Iranian clay. Kaolin. yellow clay , brown clay. Also the effecl of acid has been studied to&#x0D; activate and improve the adsorption process in the decolorization ol dark lubricant oil. The adsorption&#x0D; isotherms data obtained rvere found to follow the Freundiich adsorption isotherm model.

Recovery and fate of three species of marine dinoflagellates after yellow clay flocculation

The recovery and fate of three species of dinoflagellates, Alexandrium tamarense, Cochlodinium polykrikoides and Scrippsiella trochoidea, after having been sedimented by yellow clay, were investigated in the laboratory. The effect of burying period in yellow clay pellet and mixing on the recovery of settled algal cells were studied. The morphological changes of algal cells in yellow clay pellet were also tracked. Results showed that there was almost no recovery for A. tamarense and C. polykrikoides, and the cells decomposed after 2-3 days after visible changes in morphology and chloroplasts. There was some recovery for S. trochoidea. Moreover, S. trochoidea cysts were formed in clay pellet during the period of about 14 days, with the highest abundance of 87 000 cysts g(-1) clay and the incidence of cyst formation of 6.5%, which was considered as a potential threat for the further occurrence of algal blooms. S. trochoidea cysts were isolated from yellow clay and incubated to test their viability, and a germination ratio of more than 30% was obtained after incubation for 1 month. These results showed the species specificity of the mitigation effect of yellow clay. It is suggested that cautions be taken for some harmful species and thorough risk assessments be conducted before using this mitigation strategy in the field.

Jeremiah Puckett

Jeremiah Puckett We carried him to the highland of no-time, A place as lonesome as the caw of crow, Up the sawbriared mountain of slow-climb To reach the place he'd chosen long ago To stay until the prophesy of fire— The second-coming came to claim his soul— Awaiting then the year, the day, the hour He wanted those who brought him here to know He'd be no burden on this mountain's top Nor to those of after-come be in their way Waiting in land too poor to make a crop, Sandstone rock and yellow mountain clay. Salvation his by grace, we left him there Tucked on the mountain to a wind-made prayer. —Billy C. Clark 100 ...

Late quaternary vegetation dynamics and human impact on Alexander Selkirk Island, Chile

AbstractAim To reconstruct the history of vegetation and environments using pollen, charcoal and sediment analysis, and to identify the timing and nature of climate change and human impact on the vegetation of a remote Pacific island.Location Cerro de Los Inocentes, 1000 m above sea level, Alexander Selkirk Island (33°45′S, 80°45′W), Chile. The westernmost island of the Juan Fernandez Archipelago, south‐east Pacific Ocean.Methods A 150‐cm long sediment core comprising 87 cm dark brown peat overlying 63 cm of yellow grey clay was extracted from a shallow depression on the southern slopes of Cerro de Los Inocentes. Pollen, charcoal, sediment and accelerator mass spectrometry radiocarbon analyses were used to construct a record of vegetation change through time. Numerical analysis of multispecies data allowed the classification of fossil assemblages into distinct pollen zones.Results Pollen and spores are preserved throughout the sediment with high concentrations coinciding with the beginning of organic sediment accumulation at around 8000 14C yr BP. Prior to 8000 14C yr BP, the deposition of clays, presumably from upslope erosion, occurred in a landscape sparsely vegetated by grasses, ferns and Pernettya rigida heath, including several plants that are only found 100–200 m above the site today (Zone CI‐1). After 8000 14C yr BP, a P. rigida heath was the dominant vegetation (Zone CI‐2). A shift to a wet heath–shrubland (Zone CI‐3) occurred at 6000 14C yr BP and was followed by a transition to a treefern–shrubland mosaic accompanied by periodic burning (Zone CI‐4) after 4500 14C yr BP. The impact of human occupation is evident in Zone CI‐5 at 450 14C yr BP with the loss of forest species, increased burning and invasion of the exotic plant Rumex.Main conclusions The pollen and charcoal record provides the first evidence of vegetation changes spanning at least the last 8000 14C yr BP from the high altitude environment of Alexander Selkirk Island. Prior to 8000 14C yr BP, the altitudinal ranges of different plant species may have been suppressed by a cooler and drier climate. Increasing precipitation and temperatures at the end of the last glacial period may have mobilized exposed sediments in a sparsely vegetated upland environment, altering local drainage patterns, eventually leading to slope stabilization and deposition of organic detritus under an increasing density of heath and shrub vegetation. The subalpine heath–shrubland persisted until 4500 14C yr BP when first evidence for sustained burning is found in association with the establishment of a more open treefern–shrubland vegetation pattern. In the absence of human occupation at this time, the influence of increased climatic variability associated with more frequent El Niño‐Southern Oscillation events during the mid to late Holocene is considered one of the main driving forces behind increased vegetation disturbance during this period. The record provides evidence that island vegetation patterns have been highly dynamic over millennial to decadal time‐scales and that the flora has persisted through periods of rapid and major climate change. This changed with the discovery of the island by European explorers in the late sixteenth century and the subsequent introduction of goats and exploitation and burning of forests, which resulted in the progressive destruction of native vegetation and the invasion of introduced plants. There is evidence that reduced burning and control of the goat population within the last 50 years has resulted in marginal recovery of some high altitude native plant species.

Structure degradation and changes in the mechanical behaviour of a stiff clay due to weathering

The paper discusses the results of research into the causes of weathering of stiff Pleistocene clays located in the Montemesola Basin (TA, Italy), and on the effects of weathering on the clay's mechanical behaviour. The weathered clays are yellow-brown and overlie the original grey clays in the whole basin. The liquidity indexes of both the yellow and the grey clays, their fabric, as observed by means of scanning electron microscopy, as well as the yellow clay oxidation features suggest that drying has been the main weathering process in the basin. This is confirmed by the results of drying–wetting cycle tests carried out in the laboratory on undisturbed clay samples, which show the drying–wetting cycles to produce changes in the grey clay similar to those present in situ due to weathering. Results of oedometer, stress path and triaxial tests show that weathering has caused a degradation of the clay bonding and an associated reduction in the size of the clay state boundary surface. Both one-dimensional and iso-tropic compression data and the shear data indicate that the effects of weathering on the mechanics of the clay may be established according to the decrease in the clay stress sensitivity. Weathering also causes a decrease in the normalised shear stiffness, as observed by means of bender element tests, which is also related to a decrease in the stress sensitivity.

Powdered granite is not an effective fertilizer for clover and wheat in sandy soils from Western Australia.

Granite (silicate) rock dust, a by-product of quarry operations, is being advocated and used as a fertilizer in the wheatbelt of south-western Australia (WA). The dust is insoluble and based on its nutrient element content (1.9% K and 0.3%P and negligible N) it is not expected to be a useful fertilizer. Previous laboratory studies and glasshouse experiments in WA suggest the dust is a slow release K fertilizer. This paper extends the previous studies to consider the dust as an NP or K fertilizer in the year of application in a field experiment on a soil deficient in N, P and K. In addition, the effectiveness of the dust as a K fertilizer was compared with the effectiveness of KCl (muriate of potash), the K fertilizer used in WA at present, in glasshouse experiments using K deficient soils. In the field experiment, compared with NP fertilizer or NPK fertilizer (urea, supplying N; superphosphate, providing P, S, Ca, Cu, Zn and Mo; KCl providing K), the dust had no effect on grain yield of wheat (Triticum aestivum); in fact dust applied at 20 t ha-1, for unknown reasons, reduced yields by about 65% compared to the nil (no fertilizer, no dust) treatment. Relative to the nil treatment, applying NPK fertilizer increased yields about threefold, from 0.54 to 1.79 t ha. The glasshouse experiments showed that, relative to KCl, the dust was from about 0.02 to 14% as effective in K deficient grey sandy soils for producing dried tops of 30-day old wheat plants or 42-day old clover (Trifolium subterraneum) plants. In soils with adequate K (yellow sands, sandy loams or clays, loamy clays, clay loams and clays), neither KCl nor the dust affected yields of 30 to 42-day old wheat or clover plants grown in the glasshouse. In the glasshouse experiments, no yield depressions were measured for the dust applied up to 17 g dust per kg soil (equivalent to 17 t dust ha-1 mixed into the top 10 cm of soil in the field). It is concluded that the dust has no value as a fertilizer.

Origins and applications of size fractions of soils overlying the Beasley Creek gold deposit, Western Australia

Primary mineralisation at the Beasley Creek Au deposit, hosted in black shales within mafic and ultramafic rocks, was sulphide- and trace element-rich. The deposit subcrops beneath soil within a small window of deeply weathered Archaean basement in the northeast Yilgarn Craton of Western Australia, surrounded by extensive colluvial–alluvial plains. Regolith overlying the mineralisation and its host sequence is comprised of ferruginous saprolite and some duricrust, overlain by red–brown soil which is strewn with residual ferruginous lag. The colluvial–alluvial wash plains around the weathered basement window are mantled by a thicker red–brown soil, strewn with polymictic lag. Soil samples and surface lag were collected along two traverses across the mineralisation with the aim of determining the optimum geochemical sampling medium for exploration. The 710–4000 μm soil fraction consists largely of black goethite- and hematite-rich nodules, red to yellow ferruginous clay granules, minor quartz, calcrete and, close to subcropping mineralisation, scarce gossan fragments. In contrast, the 75–710 μm fraction, which appears to be largely aeolian in origin, consists mainly of red–brown hematite-coated sand grains, minor feldspar, and small, ferruginous granules. The largely aeolian 4–75 μm fraction is composed mostly of quartz, with minor kaolinite and Fe oxides. A clay-rich <4 μm fraction was removed from the <75 μm material by dispersion in water and sedimentation. The complete soil and the 710–4000, 4–75, and <4 μm fractions were compared as sampling media. Due to its dominant wind-blown quartz component, the 75–710 μm fraction was discarded. The 710–4000 μm fraction, and the fine lag derived from it, are the most effective geochemical sampling media. The distributions of As, Au, Cd, Cu, Sb, Se, W and Zn in this soil fraction are related to mineralisation. Gold gives a 600-m-wide anomaly of >20 ppb, locally reaching 200–300 ppb. The black shales, which host the mineralisation, are indicated by maxima in Ba and Mn. The 4–75 μm fraction is a significantly less effective sample medium than the <4 μm fraction due to dilution by aeolian silt. The <4 μm fraction indicated the host phyllite by an increase in sericite; the phyllites and duricrusts were indicated by an increase in kaolinite. Dispersions of Au, As, Cd and Cu in the <4 μm fraction show that it is also a useful sampling medium.

Pedogenic and diagenetic influences on void coating formation in Lower Cretaceous paleosols of the Mill Creek Formation, southwestern Alberta, Canada

Pedogenic and diagenetic influences on void coating formation were studied in two paleosols from the Lower Cretaceous (Albian) Mill Creek Formation in southwestern Alberta, Canada, using detailed micromorphological, mineralogical and geochemical methods. The paleosols consist of alternating decimetre-scale beds of red, grey-green and variegated mudstone. Intermediate horizons (red and grey-green variegated mudstones) contain associations of pale yellow clay coatings, dark red clay coatings, Fe-depletion hypo-coatings and Fe-oxide quasi-coatings. SEM–EDX-ray analyses indicate that the dark reddish coatings are dominated by Si, Al and Fe, with subordinate amounts of K, Na, Ca, Mg and Ti. Pale yellow clay coatings have a higher Si content, and lower Al, K, Na, Ca and Fe contents relative to reddish coatings. Within the paleosol profiles, the distribution of clay minerals indicates: (1) an increase in discrete clay minerals downward, (2) a decrease in mixed layer illite-smectite downward and (3) an increase in chlorite upward. X-ray diffraction indicates that the pale yellow and dark red clay void coatings are polymineralic. Pale yellow clay coatings have a higher proportion of mixed layer illite–smectite and kaolinite, less chlorite and are less crystalline than dark reddish coatings. Despite a diagenetic overprint, including development of diffusion gleyans, degradation of organic matter, burial reddening, and probably some smectite illitization, both compositional and morphological gradients exist in the paleosol profiles and void coatings. These gradients are most likely related to depositional variations and to pedogenic development in the original soils under variable Eh–pH conditions in the presence of organic matter. Therefore, although the void coatings are altered (diagenetic features) their morphology, mineralogy and perhaps even some of their microchemistry is attributable to the presence of pedogenic precursors initially formed in soils similar to modern, temperate Alfisols and glossic soils.

New uses for brick-making clay materials from the Bailén area (southern Spain)

AbstractAn attempt has been made to assess new potential applications for the Bailén clays, traditionally used for manufacturing bricks, based on mineralogical, chemical, particle size, plasticity and firing results. Raw materials and mixtures used by the local factory were selected and tested with the addition of some diatomite, feldspar or kaolin. Based on their properties, clay materials from Bailén might be suitable for making porous red wall tiles, clinker, vitrified red floor tiles and porous light-coloured wall tiles by pressing; the first could be manufactured from the raw materials and mixtures currently used by the local manufactures. On the other hand, stoneware shaped by extrusion, such as perforated bricks, facing bricks and roofing tiles, can be also manufactured from the mixtures used at the factory if they contain 20-25% carbonate and small amounts of iron oxides; lightweight bricks require black and yellow clays with diatomite.

Clay illuviation in Red Mediterranean soils

Theories regarding pedogenesis in Red Mediterranean soils have undergone several stages of development. The concept of clay illuviation in these soils was not a part of early theories and it is not yet unanimously accepted as a leading soil forming process. A methodology is presented for studying the illuviation of clay in these soils emphasizing typology of textural features and fabrics. The problem of age determination is also addressed, through the use of radiometric dates and correlation with archaeological artifacts. Clay illuviation in Red Mediterranean soils under present day environmental conditions suggests that it occurs presently only on humid and sub-humid margins of the Mediterranean basin. Elsewhere illuvila clay accumulations are inherited from Interglacial periods. Red Mediterranean soils during glacial periods were eroded, coluviated, aggraded with aeolian dust, calcitic fraction of which was redistributed in form of calcitic features and eventually were affected by water logging. An example of water logging of Red Mediterranean soils (Mamora, Morocco) which took place during the last Glacial cycle, consists of yellow illuvial clays accompanied by a yellowing of the ground mass. During earlier cycles water logging resulted in whitish grey stains in which hydromorphic textural features were deposited.

The cretaceous/paleogene boundary and planktonic foraminifera in the flyschgosau (Eastern Alps, Austria)

The studied interval extends from 2.5 m below to 1 m above the Cretaceous/Paleogene (K/P) boundary and comprises the uppermost Maastrichtian marly limestone overlain by a boundary (rusty) layer—a dark yellow orange clay 5–10 mm thick, followed by a turbidite sequence of very fine sandstones and grey-brown marls. The following planktonic foraminiferal zones are distinguished: Abathompalus mayaroensis, PO (subzones: POa— Guembelitria cretacea and POb — Globoconusa conusa), Pa or Parvularugoglobigerina eugubina and P1 (subzone: P1a or Subbotina pseudobulloides). The distribution of iridium shows a relatively sharp rise to a maximum value of 7.176 ppb about 1.2 cm above the rusty layer, followed by a rapid drop to normal background levels. The Abathomphalus mayaroensis Zone exhibits a moderately diverse planktonic foraminiferal assemblage. The main extinction episode occurs within the rusty layer; only a few species survived. Survivors are small primitive forms. The first new Paleocene species evolved immediately after the major Cretaceous extinctions. Rapid extinction of planktonic foraminifers coincides with the iridium anomaly which suggests that, at this site, the source(s) of the iridium anomaly was (were) probably responsible for K/P extinctions.

Symbiont effectof rhizobiumbacteria and vesicular arbuscular mycorrhizal fungi onPisum sativumin recultivated mine spoils

The frequency (F%) of spontaneous endomycorrhizal fungal infection (AMF) and the root nodulation of Pisum sativum L. was studied after 8 and 15 years of recultivation in 4 soils (andesitic tuff, yellow sand, yellow clay, and grey clay) disturbed by mining activities. The effects of Rhizobium inoculation and the interaction of both microsymbionts with plant production were also examined, along with humus content and the humus stability coefficient, in the following variations: control, NPK fertilizer, NPK + lignite, NPK + straw, and sewage sludge. Dump spoils originating from deep geological layers were poor in organic materials. After 12 years of recultivation, the humus content increased significantly. No such increase was noted in grey clay and the natural, brown forest soil used as an undisturbed (control) sample. The degradation of soils by mining brings about a decrease in the rhizobial and mycorrhizal population, so the number of spontaneous Rhizobium nodules is relatively low and does not influence the yield of peas. Inoculation with a selected, effective strain of Rhizobium leguminosarum bv. viceae, however, enhanced dry matter production in these microbiologically degraded soils. Although the frequency of AMF infection was also higher after rhizobial inoculation, no positive correlation was found between dry matter production of peas and the F% of AMF. Spoils treated with lignite, straw, and sewage sludge had an especially high level of spontaneous mycorrhizal populations, indicating that organic materials had a favorable effect on the recultivation processes and fertility of mine spoils.

The failure of Carsington Dam

The upstream slope of Carsington Dam failed just before its completion in 1984. The slip started on the right abutment and spread across the valley to a length of nearly 500m. Extensive investigations were conducted, and further information was obtained when the dam was reconstructed. The initial slip sheared through the core, which contained shear surfaces due to rutting, and along a layer of Yellow Clay which contained solifluction shears. Both materials were brittle, with low residual strengths. The factor of safety based on measured peak strengths was about 1·4; with reductions to allow for shears it was 1·2. It had been reduced to 1·0 by progressive failure. Finite element (FE) analyses in which strain-softening was reproduced confirmed this. It was concluded that the slide spread by lateral load transfer, through sections of the dam with a safety factor greater than 1. In the vailey centre, the slide passed through the base of the mudstone fill. A combination of FE and limit equilibrium analysis indicated that the factor of safety just before collapse was about 1·1. The factor of safety was 1·6 with intact strengths and 1·4 after allowance for shears. The reduction to 1·1 was due to progressive failure; from 1·1 to 1·0 it was due to lateral load transfer. La pente amont du barrage de Carsington s'est écroulée en 1984 juste avant son achèvement. Le glissement a commencé sur le contrefort droit et s'est propagé au travers de la vallée sur une longueur d'environ 500 m. Des études approfondies ont été menées et des informations complémentaires ont été obtenues lors de la reconstruction du barrage. Le glissement initial s'est propagé par cisaillement au travers du noyau, où l'on observe des surfaces de cisaillement dues à des stries, ainsi qui le long d'une couche d'argile jaune qui présente des cisaillements de solifluxion. Les deux matériaux présentaient des comportements fragiles, à faibles résistances résiduelles. Le facteur de sécurité, calculé à partir des contraintes maximales mesurées, était égal à environ 1,4. Il a été réduit à 1,2 en raison du cisaillement, puis à 1,0 par suite de la rupture progressive. Une analyse par éléments finis, reproduisant la relaxation des déformations, confirme ces résultats. Il apparaît qui le glissement s'est propagé par transfert latéral de la charge à travers des sections du barrage à facteur de sécurité supérieur à 1,0. Au centre de la vallée, le glissement a traversé la base du remblai de mudstone. Les analyses par élément finis combinées aux analyses par équilibres limites montrent que le facteur de sécurité était de l'ordre de 1,1 juste avant la rupture. Il était égal à 1,6 pour les contraintes originelles et à 1,4 lors de l'apparition du cisaillement. La réduction jusqu'à 1,1 est due à la rupture progressive; De 1,1 à 1,0, elle est due au transfert latéral de la charge.

Progressive failure of the Carsington Dam: a numerical study

The mechanism of progressive failure is well understood as one which involves nonuniform straining of a strain-weakening material. Traditional limit equilibrium analysis cannot be used alone to obtain a rational solution for progressive failure problems because the deformation of the structure must be taken into account in the analysis. The failure of the Carsington Dam during construction in 1984 has been attributed to progressive failure of the underlying yellow clay and the dam core materials. The dam was monitored extensively prior to failure, and an elaborate geotechnical investigation was undertaken after failure. The limit equilibrium analysis indicated that the factors of safety were over 1.4 using peak strength of intact clay material or 1.2 based on reduced strength accounting for preshearing of the yellow clay layer. Factors of safety were found to be less than unity if residual strengths were used. The actual factor of safety at failure was, of course, equal to one. By using the finite element analysis with strain-weakening models, the extent and degree of weakening along the potential slip surface were calculated. The calculated shear strength was then used in the limit equilibrium analysis, and the factor of safety was found to be 1.05, which is very close to the actual value of 1.0. More importantly, the mechanism of failure and the initiation and propagation of the shear zones were captured in the finite element analysis. It was also found that accounting explicitly for pore-water pressure effects using the effective stress approach in the finite element and limit equilibrium analyses provides more realistic simulations of the failure process of the structure than analyses based on total stresses. Key words : progressive failure, strain softening, finite element analysis, dams.

The abundance and diversity of earthworms in pasture soils in the fleurieu peninsula, south australia

Earthworms were surveyed in 113 pasture soils in the Mount Lofty Ranges, Fleurieu Peninsula, South Australia, in a region where annual rainfall is 600–1200 mm and the climate is mediterranean. The soils within these pastures included a variety of profile forms (e.g. sandy soils with yellow, brown or red clays in the B horizon; uniform coarse textured sands). The most widespread earthworm species were Aporrectodea trapezoides (found at 95% of sites), Microscolex dubius (61%), Aporrectodea rosea (38%) and Aporrectodea caliginosa (36%). These are all introduced species. The total densities of earthworms varied from 0 to 608 m −2 (mean = 169.2). At most sites (66%), densities were <200 m −2. Native earthworms were present at 40 sites but their total densities exceeded 100 m −2 at only 7 sites. The species richness and diversity of the earthworm communities were low; never more than 5 species were found in any one pasture (mean = 3.1). The abundance of the introduced species (all species combined) varied between soil profile forms, being least in the uniform sands. No such variation was found for native species. Several significant, but weak, correlations were obtained between the numbers and weights of earthworms and other environmental variables (e.g. rainfall, depth of A horizon, % sand, clay. nitrogen and carbon). Stepwise multiple regression of the numbers and weights of introduced species against these environmental variables suggested that % clay was the most important regressor. The potential for increasing the abundance and diversity of earthworms in Australian soils is discussed.