Investigations of Cretaceous and Tertiary kerogens in sediments of ODP Leg 113 holes

Seventy-one samples from nine sites were analyzed for total organic carbon (TOC). Fifty-six samples, containing 0.2% or more TOC, were evaluated by Rock-Eval to assess the nature of their kerogen and its petroleum source potential. Visual kerogen studies were carried out. Petroleum potential was encountered only in Valanginian calcareous claystones at Hole 692B close to the margin of Dronning Maud Land. A section of 44.7 m was penetrated. The unit possesses a revised mean TOC of 9.8% and petroleum potential of 43.2 kg/Mg, relatively high values in comparison to other Cretaceous anoxic oceanic sections and the totality of petroleum source rocks. At Sites 689 and 690, extremely low TOC levels, mean 0.07%, preclude kerogen analysis. Kerogens in Eocene to Pliocene sediments of the central and western Weddell Sea (Sites 694, 695, 696, and 697) are similar everywhere, largely comprising brown to black, granular, amorphous material of high rank, and generally possessing several reflectance populations of vitrinite particles. The latter are interpreted as indicative of the recycling of sediments of a variety of levels of thermal maturity.

Consolidation tests of ODP Leg 113 samples

Examination of the geotechnical characteristics of Weddell Sea, Maud Rise, and South Orkney microcontinental margin sediments recovered during ODP Leg 113 reveals that the reduction in porosity (consolidation) of the siliciclastic, calcareous, and diatomaceous sediments is primarily a process governed by vertical stresses created by overburden. The initial porosity of the sediments in these areas is governed by the amount of diatoms present. The more diatoms, the higher the porosity. Surficial diatom-rich sediments are everywhere overconsolidated. This is attributed to the strong microfabric created by the diatoms, calcareous and clay particles. The deeper diatom-free sediments of Maud Rise range from slightly underconsolidated to normally consolidated. The silty clays and clays of the Weddell Sea and South Orkney margin are underconsolidated. The degree of underconsolidation of these sediments is similar to that determined in a number of different locations throughout the world's oceans. The very low permeability of the Weddell Sea and South Orkney margin sediments appears to account for this underconsolidation.

Calcium carbonate concentrations of ODP Sites 113-689 and 113-690

An almost continuous Upper Cretaceous through Pleistocene biogenic sediment section was recovered from two sites on Maud Rise, a volcanic edifice in the Weddell Sea, off eastern Antarctica. Calcium carbonate values were determined for 1100 closely spaced samples using a Coulometrics CO2 Coulometer. Following a very brief decrease in the percentage of calcium carbonate immediately above the Cretaceous/Tertiary boundary, values remain high (~70%-80%), throughout most of the Paleocene, with variations primarily attributed to changes in the relative abundance of terrigenous and biogenic components. A small general decrease in calcium carbonate is observed from the upper Paleocene to lower middle Eocene. Eocene values continue to show small to moderate fluctuations. These fluctuations become more pronounced in the Oligocene as biosiliceous and carbonate sediments are mixed and interlayered. A distinct decrease in the calcium carbonate component is observed in the upper Oligocene through lower middle Miocene. Calcium carbonate becomes dominant again in the middle and lower upper Miocene, followed by almost exclusive biosiliceous sedimentation until the Pleistocene, where foraminifer-dominated calcareous ooze was recovered. Interpretation of this data will be carried out when a more finalized chronostratigraphy for the sequence has been produced.

Eocene-Oligocene calcareous nannofossil events of ODP Sites from the Southern Ocean

The evolution of the Southern Ocean climate during the late Eocene-late Oligocene interval is examined through highresolution, quantitative calcareous nannofossil analyses on samples from the Southern Ocean sections on Maud Rise and Kerguelen Plateau. We determined the abundance patterns of the counted species to clarify the biostratigraphy, which we correlated with high-resolution magnetostratigraphy [Roberts, A.P., Bicknell, S.J., Byatt, J., Bohaty, S.M., Florindo, F., Harwood, D.M., 2003a. Magnetostratigraphic calibration of Southern Ocean diatom datums from the Eocene-Oligocene of Kerguelen Plateau (Ocean Drilling Program Sites 744 and 748). In: Florindo, F., Cooper, A.K., O'Brien, P.A. (Eds.), Antarctic Cenozoic Palaeoenvironments: Geologic Record and Models. Palaeogeogr., Palaeoclimatol., Palaeoecol. 198 145-168; Florindo, F., Roberts, A.P., in press. Eocene-Oligocene magnetobiochronology of ODP Sites 689 and 690, Maud Rise, Weddell Sea, Antarctica. Geol. Soc. Am. Bull.], and used this data to interpret paleoceanographic changes through the late Eocene to late Oligocene. Percentage plots of the individual species, compared with R-mode principal component and cluster analysis results, allowed us to divide the assemblages into three groups: temperate-water taxa, cool-water taxa, and no temperature-affinity taxa. We attempt correlations between these paleoecological groups and the major sea-surface temperature (SST) variations with tectonic and paleoceanographic changes in the Southern Ocean. During the late Eocene, the nannofossil assemblage data reveal that there were several minor SST decreases (coolings) from 36 to 34 Ma, before the Eocene/Oligocene (E/O) boundary. A sharp cooling event, dated at 33.54 Ma (earliest Oligocene), occurred about 160 kyr after the E/O boundary, which is dated at 33.7 Ma. Relatively stable, cool conditions are interpreted to persist until the latest Oligocene, when an increase in abundance of temperate-water taxa, which corresponds to an antithetical decrease in abundance of cool-water indicators, is recorded. On the basis of our dating, the opening of the Drake Passage, allowing shallow-water circulation, began by 33.54 Ma at the latest, while the establishment of deep-water connections through the Tasmanian Gateway occurred at 33 Ma, as suggested by Exon et al. [Proc. ODP, Init. Rep. 189 (2001) 1].

(Table 1) Types of giant magnetofossils in ODP holes

Magnetotactic bacteria biomineralize magnetic minerals with precisely controlled size, morphology, and stoichiometry. These cosmopolitan bacteria are widely observed in aquatic environments. If preserved after burial, the inorganic remains of magnetotactic bacteria act as magnetofossils that record ancient geomagnetic field variations. They also have potential to provide paleoenvironmental information. In contrast to conventional magnetofossils, giant magnetofossils (most likely produced by eukaryotic organisms) have only been reported once before from Paleocene-Eocene Thermal Maximum (PETM; 55.8 Ma) sediments on the New Jersey coastal plain. Here, using transmission electron microscopic observations, we present evidence for abundant giant magnetofossils, including previously reported elongated prisms and spindles, and new giant bullet-shaped magnetite crystals, in the Southern Ocean near Antarctica, not only during the PETM, but also shortly before and after the PETM. Moreover, we have discovered giant bullet-shaped magnetite crystals from the equatorial Indian Ocean during the Mid-Eocene Climatic Optimum (~40 Ma). Our results indicate a more widespread geographic, environmental, and temporal distribution of giant magnetofossils in the geological record with a link to "hyperthermal" events. Enhanced global weathering during hyperthermals, and expanded suboxic diagenetic environments, probably provided more bioavailable iron that enabled biomineralization of giant magnetofossils. Our micromagnetic modelling indicates the presence of magnetic multi-domain (i.e., not ideal for navigation) and single domain (i.e., ideal for navigation) structures in the giant magnetite particles depending on their size, morphology and spatial arrangement. Different giant magnetite crystal morphologies appear to have had different biological functions, including magnetotaxis and other non-navigational purposes. Our observations suggest that hyperthermals provided ideal conditions for giant magnetofossils, and that these organisms were globally distributed. Much more work is needed to understand the interplay between magnetofossil morphology, climate, nutrient availability, and environmental variability.

Depth ranges of calcareous nannofossil datums from ODP Holes 113-689B and 113-690B

Magnetostratigraphic studies of Paleogene sediments piston-cored on Maud Rise, Weddell Sea (ODP Sites 689 and 690), are a cornerstone of Southern Ocean Paleogene and Neogene chronostratigraphy. However, parts of previous magnetostratigraphic interpretations have been called into question, and recent reinvestigation of the upper Paleocene-middle Eocene portion of Site 690 suggested that the records might be contaminated by spurious magnetizations, which raises doubts about the reliability of these important records. We undertook a high-resolution magnetostratigraphic study of Eocene-Oligocene u-channel samples from ODP Holes 689B, 689D, 690B, and 690C in order to address these concerns. A pervasive overprint appears to be present below the middle Eocene, which compromises magnetobiostratigraphic interpretations for the upper Cretaceous and lower Paleogene. Nevertheless, our new results provide a robust record of geomagnetic field behavior from 38.5 to 25 Ma and confirm the reliability of these sediments for calibration of biostratigraphic datum events during a crucial phase of earth history when major Antarctic ice sheets developed. Also, comparison of magnetozone thicknesses in multiple holes at the same site indicates that ~1.2-1.8 m of the stratigraphic record is missing at each core break, which corresponds to time breaks of 120-360 k.y. Lack of a continuous record within a single hole renders useless spectral analyses for investigating long geomagnetic and paleoclimatic time series. This observation reinforces the need for coring of multiple offset holes to obtain continuous paleoceanographic records. Sedimentary hiatuses have been identified only at the deeper of the two investigated sites (Site 690), which could mark a local response to the onset of the Antarctic Circumpolar Current.

Sapientia, 1974, Vol. XXIX, nº 113 (número completo)

Contenido: El Esse y el Intelligere divino, fundamento universal e inmediato de todo ser y de toda verdad y entender participados en Santo Tomás / Octavio N. Derisi – Saint Thomas contre l’agnosticisme / F. Van Steenberghen – Trascendentalidad de la belleza en el pensamiento de Santo Tomás / José R. Sanabria -- ¿Navaja de Ockham o navaja de Santo Tomás? / J. E. Bolzán – Notas y comentarios -- Bibliografía

Diário da Constituinte [gravação de vídeo] : [programa n. 113]

O esboço da nova Constituição está pronto. Bernardo Cabral (PMDB-AM) relata que o esboço reflete exatamente o que foi decidido nas comissões temáticas. Sobre a reforma agrária, Fernando Henrique Cardoso (PMDB-SP) relata que o texto permite emendas que propiciem a manutenção da produção e o acesso à terra. Os direitos individuais também sofreram modificações e Nelson Jobim (PMDB-RS) relata que os conceitos foram bem sistematizados e fundamentados. O esboço da Constituição foi entregue ao presidente da Assembleia Nacional Constituinte (ANC), Ulysses Guimarães (PMDB-SP) e será reexaminado por todos os membros da Comissão de Sistematização da ANC. Na sessão O Povo Pergunta, cidadão quer saber como fica a questão do emprego. Domingos Leonelli (PMDB-BA) responde que houve um avanço considerável com a redução da jornada de trabalho para 40 horas semanais. José Walter Filho, coordenador do Sine-DF, diz que a questão do desemprego é estrutural e o próprio sistema estatal de emprego não chega a atender 2% do desemprego a nível nacional. Aloísio Vasconcelos (PMDB-MG) acredita que o desemprego está associado a políticas nacionais e que uma política de emprego se faz necessária, ao invés de políticas econômicas que geram emprego ou desemprego, dependendo da ocasião . Virgílio Galassi (PDS-MG) entende que o desemprego depende também do empregador. Celso Dourado (PMDB-BA) relata que deve-se evitar a política monetarista que valoriza o capital, não o trabalho. Olívio Dutra (PT-RS) afirma que dentro do capitalismo brasileiro há formas de minimizar o desemprego.

Untersuchungen am Köhler in der nördlichen Nordsee (Ergebnisse der 113. Reise des FFS "Walther Herwig")

Im Rahmen des Internationalen Jungfischprogramms des ICES untersuchten von Januar bis März 1991 Forschungsschiffe mehrerer Nationen die Jungtischbestände der Nordsee. FFS "Walther Hcrwig" beteiligte sich vom 13. Januar bis 15. Februar an diesen Untersuchungen.

Cytological aspects of gonadotropic cells and pre-opticoneurohypophysial neurosecretion during the ovarian cycle of Eudontomyzon danfordi. [Translation from: Studia Univ.Babes-Bolyai, Biologia 18 105-113, 1973.]

The connection between the activity of the gonadotropic cells of the hypophysis and the neurosecretion in the pre-optico neuro-hypophysial system in different groups of vertebrates has been examined by many authors. It has been established that in many species there exists some kind of synchronism between the sexual cycle and the cellular activity of neurosecretion, a fact that has led to the prevailing idea that gonadotropic activity in the hypophysis is regulated by the hypothalamus. This paper summarises the results of experiments made in this direction on Cyclostomata. The materials for research came from adult individuals of Eudontomyson danfordi Regan taken from the rivers Somes-Rece and Ivo (Harghita district) at different times of the year.

Mellum Island (southern North Sea): dynamic processes and sedimentary structures. I. Southern tidal flat, transition zone and high-surface.[p.72 (Blasensand) only][Translation from: Senckenbergiana Maritima 11, 59-113, 1979]

This partial translation of a longer article describes the phenomenon of ”Blasensand”. Blasensand is formed when sedimentation of dried out sand is suddenly flooded from above. A more detailed explanation of Blasensand is given in this translated part of the paper.