Composition of sulfides from the Sierra Leone Fracture Zone (Central Atlantic Ocean)

An analysis of data on the location of hydrothermal fields, seismicity, and satellite altimetry evidences that in mid-ocean ridges with low spreading rate hydrothermal fields tend to be grouped in areas with generally low seismic activity and at intersections of discontinuities and rift zones. Based on this assumption, the Sierra Leone Fracture Zone was studied in 2000 during Cruise 22 of R/V Akademik Nikolaj Strakhov. A study of gabbrodolerite and dolerite showed that sulfide ore minerals in them were formed both by hydrothermal and magmatic processes. An analysis of melt inclusions demonstrated that magmatic complexes formed from a high-temperature (1210-1255°C) low-potassium melt of the N-MORB type. Investigations of fluid inclusions revealed that gabbro and dolerite formed under influence of an active hydrothermal system at temperature 205-226°C. Thus, the Sierra Leone Fracture Zone is considered to be perspective for a discovery of a new hydrothermal field.

Geochemical composition and granulometry of ODP Hole 167-1017E sediments

Intensification of North Pacific Intermediate Water during the Younger Dryas and stadials of the last glacial episode has been advocated by Kennett and his colleagues based on studies of ventilation history in Santa Barbara Basin. Because Santa Barbara Basin is a semi-isolated marginal basin, this hypothesis requires testing in sequences on the upper continental margin facing the open-ocean of the Pacific. Ocean Drilling Program Site 1017 is located on the upper slope of southern California off Point Conception close to the entrance of Santa Barbara Basin, an ideal location to test the hypothesis of late Quaternary switching in intermediate waters. We examined chemical and mineral composition, sedimentary structures, and grain size of hemipelagic sediments representing the last 80 k.y. at this site to detect changes in behavior of intermediate waters. We describe distinct compositional and textual variations that appear to reflect changes in grain size in response to flow velocity fluctuations of bottom waters. Qualitative estimates of changes in degree of pyritization indicate better ventilation of bottom water during intervals of stronger bottom-water flow. Comparison between variations in the sediment parameters and the planktonic d18O record indicates intensified bottom-current activity during the Younger Dryas and stadials of marine isotope Stage 3. This result strongly supports the hypothesis of Kennett and his colleagues. Our investigation also suggests strong grain-size control on organic carbon content (and to less extent carbonate carbon content). This, in turn, suggests the possibility that organic carbon content of sediments, which is commonly used as an indicator of surface productivity, can be influenced by bottom currents.

Conflicto político, demografía y modo de producción en la Antigua Roma, siglos II-I a.C

Este trabajo se propone analizar críticamente algunas teorías recientes sobre las consecuencias sociales de la Segunda Guerra Púnica (218-201 a. C.) en la antigua sociedadáromana. Mientras que laáinterpretación clásica había subrayado el efecto dañino que las guerras de expansión supusieronápara el campesinado romano, los nuevos enfoques en boga se caracterizan por dejar de lado las contradicciones del proceso histórico, adoptando una interpretación malthusiana en la cual laápoblación simplementeáhabría crecido mucho más que los recursos para sostenerla. Considerando que la demografía no es una variable independiente sino que se encuentra enmarcada en un modo de producción específico, se propone estudiar algunasálimitaciones de los enfoques mencionados paraáluego abordar el problema desde una óptica que enfatice en la dinámica contradictoria de la sociedad romana

Composition of hardgrounds and of pore-water parameters in ODP Holes 166-1008 and 166-1009

Mineralogic, petrographic, and geochemical analyses of sediments recovered from two Leg 166 Ocean Drilling Program cores on the western slope of Great Bahama Bank (308 m and 437 m water depth) are used to characterize early marine diagenesis of these shallow-water, periplatform carbonates. The most pronounced diagenetic products are well-lithified intervals found almost exclusively in glacial lowstand deposits and interpreted to have formed at or near the seafloor (i.e., hardgrounds). Hardground cements are composed of high-Mg calcite (~14 mol% MgCO3), and exhibit textures typically associated with seafloor cementation. Geochemically, hardgrounds are characterized by increased d18O and Mg contents and decreased d13C, Sr, and Na contents relative to their less lithified counterparts. Despite being deposited in shallow waters that are supersaturated with the common carbonate minerals, it is clear that these sediments are also undergoing shallow subsurface diagenesis. Calculation of saturation states shows that pore waters become undersaturated with aragonite within the upper 10 m at both sites. Dissolution, and likely recrystallization, of metastable carbonates is manifested by increases in interstitial water Sr and Sr/Ca profiles with depth. We infer that the reduction in mineral saturation states and subsequent dissolution are being driven by the oxidation of organic matter in this Fe-poor carbonate system. Precipitation of burial diagenetic phases is indicated by the down-core appearance of dolomite and corresponding decrease in interstitial water Mg, and the presence of low-Mg calcite cements observed in scanning electron microscope photomicrographs.

Conflicto político, demografía y modo de producción en la Antigua Roma, siglos II-I a.C

Este trabajo se propone analizar críticamente algunas teorías recientes sobre las consecuencias sociales de la Segunda Guerra Púnica (218-201 a. C.) en la antigua sociedadáromana. Mientras que laáinterpretación clásica había subrayado el efecto dañino que las guerras de expansión supusieronápara el campesinado romano, los nuevos enfoques en boga se caracterizan por dejar de lado las contradicciones del proceso histórico, adoptando una interpretación malthusiana en la cual laápoblación simplementeáhabría crecido mucho más que los recursos para sostenerla. Considerando que la demografía no es una variable independiente sino que se encuentra enmarcada en un modo de producción específico, se propone estudiar algunasálimitaciones de los enfoques mencionados paraáluego abordar el problema desde una óptica que enfatice en la dinámica contradictoria de la sociedad romana

Geochemical parameters of bottom sediments from the Stromboli Canyon

In recent sediments of the Stromboli Canyon sides features of mineral and grain size compositions, redox conditions, behavior of Fe, Mn, organic carbon, Mo, and W in an environment of active input of pyroclastic material are considered. Differences in conditions of sedimentation and early diagenesis in the east and west sides of the canyon depending on position of the prevailing direction of drift and steepness of the slopes, as well as types of differentiation of detrital material in sediments under conditions of permanent vibrations are specified.

Conflicto político, demografía y modo de producción en la Antigua Roma, siglos II-I a.C

Este trabajo se propone analizar críticamente algunas teorías recientes sobre las consecuencias sociales de la Segunda Guerra Púnica (218-201 a. C.) en la antigua sociedadáromana. Mientras que laáinterpretación clásica había subrayado el efecto dañino que las guerras de expansión supusieronápara el campesinado romano, los nuevos enfoques en boga se caracterizan por dejar de lado las contradicciones del proceso histórico, adoptando una interpretación malthusiana en la cual laápoblación simplementeáhabría crecido mucho más que los recursos para sostenerla. Considerando que la demografía no es una variable independiente sino que se encuentra enmarcada en un modo de producción específico, se propone estudiar algunasálimitaciones de los enfoques mencionados paraáluego abordar el problema desde una óptica que enfatice en la dinámica contradictoria de la sociedad romana