(Table T1) Radiolaria abundance of ODP Hole 175-1082A

A primary objective of Leg 175 was to investigate the upwelling history of the Benguela Current. Upwelling along the coast is found over the shelf in several well-established cells, as well as along the shelf-slope break, and extends over the 1000-m isobath. Streaming filaments along the coast also carry upwelled water off shore (Shannon, 1985). The upwelled nutrient-rich waters are sourced from the South Atlantic central water mass, which is a mixture of subtropical and subantarctic water masses. Below the central water mass lies Antarctic intermediate water (Shannon and Hunter, 1988, doi:10.2989/025776188784480735; Stramma and Peterson, 1989, doi:10.1175/1520-0485(1989)019<1440:GTITBC>2.0.CO;2). The upwelling system supports a robust marine community (Shannon and Pillar, 1986) where radiolarians are abundant (Bishop et al., 1978, doi:10.1016/0146-6291(78)90010-3). The endemic nature of radiolarians makes them useful in reconstructing the paleocirculation patterns. The biogeographic distribution of many species is limited by water-mass distribution. In a given geographic region, species may also have discrete depth habitats. However, their depth of occurrence can change worldwide because the depths of water masses vary with latitude (Boltovskoy, 1999). Consequently, species found at shallow depths at high latitudes (cold-water fauna) are observed deeper in the water column at lower latitudes. The low-latitude submergence of cold-water species broadens their distribution, resulting in species distributions that can cover multiple geographic regions (Kling, 1976, doi:10.1016/0011-7471(76)90880-9; Casey, doi:10.1016/0031-0182(89)90017-5; 1971; Boltovskoy, 1987, doi:10.1016/0377-8398(87)90014-4). Since radiolarian distribution is closely related to water-mass distribution and controlled by climatic conditions rather than geographic regions, similar assemblages characterize the equatorial, subtropical, transition, subpolar, and polar regions of ocean basins (Petrushevskaya, 1971a; Casey, 1989, doi:10.1016/0031-0182(89)90017-5; Boltovskoy, 1999). Numerous radiolarian species found in water masses in the Angola and Benguela Current systems have also been observed in plankton net samples, sediment traps, and surface-sediment studies in the Atlantic sector of the Southern Ocean, where they exhibited particular water-mass affinities (Abelmann, 1992a, doi:10.1007/BF00243107; Abelmann 1992b, doi:10.1007/BF00243108; Abelmann and Gowing, 1997, doi:10.1016/S0377-8398(96)00021-7). This report presents data on the radiolarian fauna recovered from Site 1082 sediments in the form of a survey of species reflecting the latitudinal migration of the Angola-Benguela Front and upwelling. The data constitute a time series of relative radiolarian abundances at very high resolution (every 20 cm) of the upper 12 m of Hole 1082A.

Stable isotope composition of carbonate components of Rhaetian shallow-water limestones of the Wombat Plateau

Stable oxygen- and carbon-isotope ratios of Rhaetian (upper Triassic) limestone samples from the Wombat Plateau, northwest Australia, were measured to explore possible diagenetic pathways that the material underwent after deposition in a shallow-water environment, before plateau submergence in the Early Cretaceous. Host sediment isotopic values cluster near typical marine carbonate values (d18O ranging from -2.57 per mil to +1.78 per mil and d13C, from +2.45 per mil to +4.01 per mil). Isotopic values of equant clear calcite lining or filling rock pores also plot in the field of marine cements (d18O = +1.59 per mil to -2.24 per mil and d13C = +4.25 per mil to +2.57 per mil), while isotopic values for neomorphic calcites replacing skeletal (megalodontid shell) carbonate material show a wider scatter of oxygen and carbon values, d18O ranging from +2.73 per milo to -6.2 per mil and d13C, from +5.04 per mil to +1.22 per mil. Selective dissolution of metastable carbonate phases (aragonite?) and neomorphic replacement of skeletal material probably occurred in a meteoric phreatic environment, although replacement products (inclusion-rich microspar, clear neomorphic spar, etc.) retained the original marine isotopic signature because transformation probably occurred in a closed system dominated by the composition of the dissolving phases (high rock/water ratio). The precipitation of late-stage equant (low-Mg?) calcite cement in the pores occurred in the presence of normal marine waters, probably in a deep-water environment, after plateau drowning. Covariance of d18O and d13C toward negative values indeed suggests influence of meteorically modified fluids. However, none of the samples shows negative carbon values, excluding the persistence of organic-rich soils on subaerial karstic surfaces (Caribbean-style diagenesis). Petrographical and geochemical data are consistent with the sedimentological evidence of plateau drowning in post-Rhaetian times and with a submarine origin of the >70-m.y.-long Jurassic hiatus.

(Table 1) Isotopes, calcite, aragonite and sample descriptions at DSDP Hole 55-433C

Calcite in the cavities and veins of igneous rocks has long been recognized as an alteration by-product (Dana, 1892). Elementary mineralogy textbooks report that the most common occurrence of aragonite is in the cavities of basalts and andesites (e.g., Kerr, 1977). Therefore, it is not surprising to find both carbonate minerals in association with the moderately to extensively altered basalt flows recovered during deep sea drilling on Suiko Seamount in the Emperor Seamount chain (DSDP Leg 55, Hole 433C). The thickness and vesicularity of the flows, along with the presence of oxidized flow tops, indicate that the basalt erupted subaerially (Site 433 Report, 1980). The stable isotopic contents of the carbonate phases filling and lining the veins and vesicles denote the environment of alteration. An isotopic study was undertaken to secure supportive evidence for a subaerial period in the development of the seamount. Also, the subsequent alteration history after submergence may be interpreted from this isotopic record.

Rare earth element contents and sources in phosphorites from Pacific seamounts

Distribution of rare earth elements (REE) was studied in phosphorites collected from seamounts at depths from about 400 to 3600 m. In general phosphorites are characterized by high REE con¬tent, by a strong negative Ce anomaly, by a slight positive Gd anomaly, and by slight enrichment in heavy REE, which is also characteristic of seawater, where, to certain extent, composition of REE depends on depth. Comparison of REE composition in phosphorites and in seawater from the Northwest Pacific by means of Q-mode factor analysis revealed that REE have been transported into the phosphorites from various water depths following submergence of the seamounts. This corresponds to paleotectonic reconstructions, but is only partially consistent with age determinations of phosphorites.

Tab. 1: Age of biogene material from the ice margin, Kofoed-Hansen Bræ and Storstrømmen

Early Holocene recession of the ice cover over Germania Land in North-East Greenland 7.5 ka B.P. brought the Inland Ice margin back to a position close to the present. Continued recession after that time lead to the formation of a "Storstrømmen Sound" which separated Germania Land from mainland Greenland in the period from about 6 to 1 ka B.P. The present filling of the approximately 100 km long sound by the glaciers of Storstrømmen and Kofoed-Hansen Bræ must therefore have taken place during the Little lce Age. In an archaeological sense this implies deterioration of the living conditions of Neo-Eskimos compared to those of Palaeo-Eskimos. The neoglacial re-formation and present existence of the glaciers as a Little Ice Age relict may imply a present-day instability in their dynamics, as demonstrated by the pulsations (surge-like behaviour) in the last part of the 20th century. An earlier Little Ice Age advance might possibly have had the same amplitude as that documented from the 20th century but its exact age and character is not known. The glacio-isostatic response of the earth's crust to the variations in the Holocene glacier load implies a relatively slow and slight emergence and subsequent submergence. The shift from emergence to submergence must have taken place between about 2 and 1 ka B.P.

Tab. 1+2: C14-dates cf the older and younger emergence periods

In the neighbourhood of Oobloyah Bay various phenomena ean be eneountered whieh point to a ularge-seale uplift of shorelines, i.e. to an emergence of 200 m. Delta terraces, deltaic fan terraces and glacio-marine sands are regarded by the author as being the most reliable evidence of this. The marine limit documented by glacio-marine sand is to be found at ~170 m a.s.l. Hints of ancient shorelines located at a higher level exist only in the shape of badly preserved raised beaches. They were classified as less reliable records of past sea-levels, due to the lack of marine fossils and/or drift wood, and furthermore because those forms had been strongly influenced by periglacial processes. Deltaic deposits are of more importance in this context. The glacio-marine deltaic sands of several terrace levels contain terrestrial plant remnants which delivered C14dates. Using these dates und the relative elevations of terraces the emergenee of the area investigated could be recorded. This occured in a series of phases (and steps) which were summarized into two periods: an early period of emergenee which took place from at least 25 300 years B.P. to later than 17 340 years B.P. and a later one from at least 12 870 years B.P. up to the present day. The emergence seems to represent a discontinuous but regular sequence of relative sea level movements without intermittent submergence. Since the deltaic fans of the early emergence period were accumulated by sediments through glacio-fluvial channels of an adjacent glacier body the appropriate location of this glacial stage for one of the glaciers delivering meltwater (Nukapingwa Glacier) could be reconstructed. This stage of the glacier appears to belong to a retreating phase of the Mid-Wisconsin (?). The later period of emergence resulted in six rather glacio-marine delta terrace generations at the mouths of the main rivers with glaciofluvial regimen debouching into the Oobloyah Bay. A connection of this emergence with the glacial history of the field area is discussed. If one may rely on the age determinations of land derived plant fossils and their application for the climatic history of the area investigated, it must be concluded that the Heidelberg Valley, to a large extent, was alreaely deglaciated 25 000 years ago. The existence of a "Cockburn"-Phase in the sense of a major readvanee in Late Wisconsin times appears to be doubtful, or has been developed rather weakly.

Expression of an ortholog of replication protein A1 (RPA1) is induced by gibberellin in deepwater rice

Internodes of deepwater rice are induced to grow rapidly when plants become submerged. This adaptation enables deepwater rice to keep part of its foliage above the rising flood waters during the monsoon season and to avoid drowning. This growth response is, ultimately, elicited by the plant hormone gibberellin (GA). The primary target tissue for GA action is the intercalary meristem of the internode. Using differential display of mRNA, we have isolated a number of genes whose expression in the intercalary meristem is regulated by GA. The product of one of these genes was identified as an ortholog of replication protein A1 (RPA1). RPA is a heterotrimeric protein involved in DNA replication, recombination, and repair and also in regulation of transcription. A chimeric construct, in which the single-stranded DNA-binding domain of rice RPA1 was spliced into the corresponding region of yeast RPA1, was able to complement a yeast rpa1 mutant. The transcript level of rice RPA1 is high in tissues containing dividing cells. RPA1 mRNA levels increase rapidly in the intercalary meristem during submergence and treatment with GA before the increase in the level of histone H3 mRNA, a marker for DNA replication.

Adventitious Root Growth and Cell-Cycle Induction in Deepwater Rice1

Deepwater rice (Oryza sativa) is adapted to survive conditions of severe flooding over extended periods of time. During such periods adventitious roots develop to provide water, nutrients, and anchorage. In the present study the growth of adventitious roots was induced by treatment with ethylene but not auxin, cytokinin, or gibberellin. Root elongation was enhanced between 8 and 10 h after submergence. The population of cells in the S phase and expression of the S-phase-specific histone H3 gene increased within 4 to 6 h. Within 6 to 8 h the G2-phase population increased. Cell-cycle activation was accompanied by sequential induction of a cdc2-activating kinase homolog, R2, of two cdc2 genes, cdc2Os-1 and cdc2Os-2, and of three cyclin genes, cycA1;3, cycB2;1, and cycB2;2, but only induction of the R2 gene expression preceded the induction of the S phase, possibly contributing to cell-cycle regulation in the G1 phase. Both cdc2 genes were expressed at slightly higher levels during DNA replication. Transcripts of the A-type cyclin accumulated during the S and G2 phases, and transcripts of the B-type cyclins accumulated during the G2 phase. Cyclin expression was induced at all nodes with a similar time course, suggesting that ethylene acts systemically and that root primordia respond to ethylene at an early developmental stage.

Geologia e petrologia da ilha de São Sebastião (Estado de São Paulo)

A ilha de São Sebastião consta principalmente de rochas alcalinas que formam um maciço de 300 km2 aproximadamente, constituindo o terceiro em área no Brasil. Apresenta-se em um "stock" alongado segundo NE-SW, encaixado em estruturas de gnais. As formações geológicas encontradas consistem em 1 - Granitos e Gnais (ARQUEANO), 2 - Eruptivas básicas (RÉTICO), 3 - Eruptivas alcalinas (JURÁSSICO) e 4 - Depósitos recentes (HOLOCENO). O método de estudo empregado foi o petrográfico e a coluna geológica estabelecida em base de dados petrográficos, tectônicos e fisiográficos. O arqueano é determinado por definição dos seus tipos petrográficos (1- gnais facoidal, 2- oligoclásio-gnais, 3- hornblenda-gnais, 4- biotita-gnais e 5- microlina-granito) idênticos aos concorrentes no considerado arqueano do Brasil meridional. O triássico (rético) é conferido às rochas básicas (diabásios e basaltos) pela sua semelhança tectônica e petrográfica com as congêneres que cortam de maneira semelhante o arqueano no continente. A "mise-en-place" das eruptivas alcalinas (1- Nordmarkito, 2- Biotita-pulaskito, 3- Pulaskito, 4- Nefelina-sienito, 5- Foiaito, 6- Essexito-foiaito, 7- Essexito e 8- Teralito) pode ser considerada jurássica devido suas relações com as eruptivas básicas referidas réticas, pois na praia do Bonete (foto 14) observa-se um dique de nordmarkito cortando outro de diabásio. As eruptivas quartzo-dioríticas (quartzo-microdiorito e quartzo-andesito) cortam as alcalinas no cume do Zabumba, indicando sua idade mais moderna que estas. Além deste fato, preenchem linhas de fraturas tectônicas recentes, como as falhas ao longo do canal de São Sebastião, indicando que a topografia deveria ser a mesma que a atual para permitir rios efusivos ao nível do canal ou que pelo menos toda a zona de extrusão estivesse, como hoje está, em superfície. Os depósitos aluviais marinhos e continentais são considerados recentes, (holocênicos) pelo favor da topografia onde se dispõe, ocupando o fundo os vales e os bordos do atual modelado costeiro, idade esta conferida em base fisiográfica. A tectônica que afetou a ilha de São Sebastião participa da que atuou em todo o litoral meridional brasileiro. Pode-se distinguir duas fases distintas: na primeira ocorreram as erupções básicas e as alcalinas subsidiárias e na segunda deram-se os falhamentos escalonados em blocos basculados para NW, com as fraturas de tensão preenchidas pelas eruptivas quartzo-dioríticas. Toda a atividade tectônica foi regulada pela direção NE-SW privilegiada da estrutura do arqueano, correspondente a antigos eixos dos dobramentos laurencianos e huronianos. A geomorfologia da ilha consta de uma antiga superfície de erosão rematada até a senilidade, - o peneplano cretáceo, hoje reduzida às cristas culminares do maciço alcalino e às satélites das estruturas gnáissicas, desnivelada pelo falhamento em blocos e ligeiramente adernada para NW devido ao basculamento. Ao lado desta topografia vestigial existe o modelado atual da ilha caracterizado por uma juventude do estágio evolutivo. Esta escultura foi inaugurada com os últimos levantamentos epirogênicos que ascenderam as eruptivas alcalinas plutônicas a mais de 1.300 m sobre o nível do mar. O modelado costeiro apresenta uma costa típica de submergência com esculturas em rias, no estágio da juventude. A presença de terraceamentos marinhos de abrasão, atualmente elevados cerca de 20 a 30 m, lembra as oscilações epirogênicas ou eustáticas do litoral.

Central compact objects and the hidden magnetic field scenario

Central compact objects (CCOs) are X-ray sources lying close to the centre of supernova remnants, with inferred values of the surface magnetic fields significantly lower (≲1011 G) than those of standard pulsars. In this paper, we revise the hidden magnetic field scenario, presenting the first 2D simulations of the submergence and re-emergence of the magnetic field in the crust of a neutron star. A post-supernova accretion stage of about 10−4–10−3 M⊙ over a vast region of the surface is required to bury the magnetic field into the inner crust. When accretion stops, the field re-emerges on a typical time-scale of 1–100 kyr, depending on the submergence conditions. After this stage, the surface magnetic field is restored close to its birth values. A possible observable consequence of the hidden magnetic field is the anisotropy of the surface temperature distribution, in agreement with observations of several of these sources. We conclude that the hidden magnetic field model is viable as an alternative to the antimagnetar scenario, and it could provide the missing link between CCOs and the other classes of isolated neutron stars.

Are pulsars born with a hidden magnetic field?

The observation of several neutron stars in the centre of supernova remnants and with significantly lower values of the dipolar magnetic field than the average radio-pulsar population has motivated a lively debate about their formation and origin, with controversial interpretations. A possible explanation requires the slow rotation of the protoneutron star at birth, which is unable to amplify its magnetic field to typical pulsar levels. An alternative possibility, the hidden magnetic field scenario, considers the accretion of the fallback of the supernova debris on to the neutron star as responsible for the submergence (or screening) of the field and its apparently low value. In this paper, we study under which conditions the magnetic field of a neutron star can be buried into the crust due to an accreting, conducting fluid. For this purpose, we consider a spherically symmetric calculation in general relativity to estimate the balance between the incoming accretion flow and the magnetosphere. Our study analyses several models with different specific entropy, composition, and neutron star masses. The main conclusion of our work is that typical magnetic fields of a few times 1012 G can be buried by accreting only 10−3–10−2 M⊙, a relatively modest amount of mass. In view of this result, the central compact object scenario should not be considered unusual, and we predict that anomalously weak magnetic fields should be common in very young (< few kyr) neutron stars.

Benthic foraminifera of surface samples and sediment cores off Senegal and Gambia, West Africa

Water depth zonation of fifty nine benthonic foraminiferal species in marine sediment surfaces has been described. Some species are combined to groups which mark particular depth zones: an upper and lower shelf-fauna, an upper and lower slope fauna, and a shelf-slope fauna. Dependence on latitude could be ascertained for Textularia panamensis, and submergence effects for Hyalinea balthica.

Observation of manganese nodules and crusts in the Blake Plateau area

In late June and July, 1967, the Deep Submergence Research Vehicle (DSRV) ALVIN, aboard its mother ship, LULU, proceeded from the spring base of operations, Nassau, to its home port of Woods Hole. During this trip, from July 2 to July 14, a series of five dives were made by ALVIN on the Blake Plateau off Georgia and South Carolina, and on the continental slope north of Cape Hatteras. One of the objectives of the dive was to investigate the manganese and phosphate deposits of the Blake Plateau.

Molecular Breeding for Rainfed Lowland Rice in the Mekong Region

In the past 20 years, the rice-breeding program in Thailand had little success in developing new cultivars to replace Kao Dawk Mali 105 (KDML105) and Kao Khor 6 (RD6) for the tainted lowland rice environments. The main reason for the poor adoption of new cultivars by farmers is the susceptibility to diseases and unacceptable grain qualities. The conventional breeding program also takes at least 15 years from initial crossing to the release of new cultivars. A new breeding strategy can be established to shorten the period for cultivar improvement by using marker-assisted selection (MAS), rapid generations advance (RGA), and early generation testing in multi-locations for grain yield and qualities. Four generation of MAS backcross breeding were conducted to transfer genes and QTL for bacterial blight resistance (BLB), submergence tolerance (SUB), brown plant hopper resistance (BPH) and blast resistance (BL) into KDML105. Selected backcross lines, introgressed with target gene/QTL, were tolerant to SUB and resistant to BLB, BPH and BL. The agronomic performance and grain quality of these lines were as good as or better than KDML105.

Effects of Photosystem II inhibiting herbicides on mangroves - preliminary toxicology trials

Mangroves are sensitive to the root application of Photosystem II inhibiting herbicides and Avicennia marina is more sensitive than other mangroves tested. Seedlings of four mangrove species, including two salt-excreting species (A. marina and Aegiceras corniculatum) and two salt-excluding species (Rhizophora stylosa and Ceriops australis) were treated with a range of concentrations of the herbicides diuron, ametryn and atrazine. Assessment of responses required the separation of seedlings into two groups: those that had only their roots exposed to the herbicides through the water (A. marina and R. stylosa) and those that had both roots and leaves exposed to herbicides through the water (A. corniculatum and C australis). Salt-excreting species in each group were more susceptible to all herbicide treatments than salt-excluding species, indicating that root physiology was a major factor in the uptake of toxic pollutants in mangroves. Submergence of leaves appeared to facilitate herbicide uptake, having serious implications for seedling recruitment in the field. Each herbicide was ranked by its toxicity to mangrove seedlings from most damaging to least effective, with diuron > ametryn > atrazine. The relative sensitivity of A. marina found in these pot trials was consistent with the observed sensitivity of this species in the field, notably where severe dieback had specifically affected A. marina in the Mackay region, north eastern Australia. (c) 2004 Elsevier Ltd. All rights reserved.