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.

Lower Cretaceous nannofossils of ODP Holes 113-682B and 113-693A

Organic-rich, moderately to sparsely nannofossiliferous Lower Cretaceous claystones ("black shales") were cored at two Ocean Drilling Program Leg 113 sites on the continental slope of East Antarctica off Dronning Maud Land. A 39 m section at Site 692 yielded a Neocomian assemblage of limited diversity with rare Cyclagelosphaera deflandrei, Diadorhombus rectus, and Cruciellipsis cuvillieri, and is probably Valanginian in age. A 70-m section at Site 693 is assigned to the Rhagodiscus angustus Zone (late Aptian-early Albian in age). The latter zone is represented at DSDP sites on the Falkland Plateau, but equivalents to the Neocomian section are absent there, probably due to a disconformity. Watznaueria barnesae is the dominant species at both ODP sites, but it shares dominance with Repagulum parvidentatum at Site 693, where they total 70%-90% of the assemblage; their dominance is attributed to a paleogeographic setting within a restricted basin rather than to postdepositional dissolution of other species. The evolutionary development of this restricted basin and its eventual ventilation in early Albian times is discussed in terms of the regional stratigraphy and the breakup and dispersal of southwestern Gondwanaland. One new species, Corollithion covingtonii, is described.

Germanium content in marine sediments

In the geosphere, germanium (Ge) has a chemical behavior close to that of silicon (Si), and Ge commonly substitutes for Si (in small proportions) in silicates. Studying the evolution of the respective proportions of Ge and Si through time allows us to better constrain the global Si cycle. The marine inventory of Ge present as dissolved germanic acid is facing two main sinks known through the study of present sediments: 1) incorporation into diatom frustules and transfer to sediments by these "shuttles", 2) capture of Ge released to pore water through frustule dissolution by authigenic mineral phases forming within reducing sediments. Our goals are to determine whether such a bio-induced transfer of Ge is also achieved by radiolarian and whether Ge could be trapped directly from seawater into authigenic phases with no intervention of opal-secreting organisms (shuttles). To this end, we studied two Paleozoic radiolarite formations and geological formations dated of Devonian, Jurassic and Cretaceous, deposited under more or less drastic redox conditions. Our results show that the Ge/Si values observed for these radiolarites are close to (slightly above) those measured from modern diatoms and sponges. In addition, our results confirm what is observed with some present-day reducing sediments: the ancient sediments that underwent reducing depositional conditions are authigenically enriched in Ge. Furthermore, it is probable that at least a part of the authigenic Ge came directly from seawater. The recurrence and extent (through time and space) of anoxic conditions affecting sea bottoms have been quite important through the geological times; consequently, the capture of Ge by reducing sediments must have impacted Ge distribution and in turn, the evolution of the seawater Ge/Si ratio.

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.