Geochemistry at DSDP Hole 76-534A

At Site 534 in the Blake-Bahama Basin, western North Atlantic, an interval of 68 m of Maestrichtian (Upper Cretaceous) and upper middle to upper Eocene sediments consists of terrigenous siltstones, mudstones, and varicolored zeolitic claystones; minor recovery of micritic limestones, porcellanites, and quartzitic chert was made at this site as well. Comparisons with other Deep Sea Drilling Project (DSDP) sites in the western North Atlantic suggest that the following formations are present in this interval: Hatteras (Maestrichtian), Plantagenet (Maestrichtian and upper Eocene), Bermuda Rise (upper middle to upper Eocene), and the basal Blake Ridge Formation (upper middle to upper Eocene). Recognition of a Tertiary interval of the Plantagenet allows that formation to be divided into lower and upper informal units. Condensation makes this formal lithostratigraphic subdivision difficult. Together the formations record marked net condensed sedimentation (average rate ca. 2.5 m/m.y.) in strongly oxidizing bottom waters. From sedimentary structures and petrography, it is inferred that the terrigenous siltstones and micritic limestones were redeposited from the continental margin by turbidity currents. Chemical data plus petrography confirm relatively high plankton productivity during the upper Eocene. Much of the nonrecovered Eocene interval may represent chert and porcellanite. Fragments recovered were formed by replacement of relatively porous calciturbidites by opal-CT and quartz. Radiolarians in interbedded claystones rich in clinoptilolite show extensive dissolution. Relative to typical hemipelagic sediments, the claystones are enriched in many metals (Cu, Ni, Zn, Pb), particularly within manganese micronodules. The metal accumulation is related to a 30-m.y. period of slow net sediment accumulation, rather than to hydrothermal enrichment or to upward mobilization of metals from the underlying reduced Hatteras black shale facies. Elsewhere in the Blake-Bahama Basin, at Site 391, 22 km to the northwest, upper Eocene facies are missing, reportedly due to deep seafloor erosion of up to 800 m of the sedimentary succession. By contrast, the discovery that this interval is preserved at nearby Site 534 points to much less extensive seafloor erosion, possibly mostly in the Oligocene, which is missing at both DSDP Sites.

Tab. 2: Grain-sizes of cobble on the surface of sanderwurzel

yResults of 13 field investigations between 1966 and 1990 of the southwestern to eastern margin of Kötlujökull and its proglacial area are summarized with respect to sandar and their formation. Generally, the results are based on sedimentological examinations in the field and laboratory, on analyses of aerial photographs, and investigations of the glacier slope. The methods permitted a more detailed reconstruction of sandar evolution in the proglacial area of Kötlujökull since 1945, of tendencies in development and of single data going back until the last decades of the 19th century. Accordingly, there existed special periods of "flachsander"-formations with raised coarsegrained "sanderwurzels" resultant from the outbreak of subglacial meltwater tunneloutlets and other periods with "hochsander-"formations by supraglacial drainage. At present the belts of hochsanders in front of the glacier come up to more than 4 m in thickness and 1000 m in width, therefore containing perhaps more sediment direct in front of Kötlujökull than the old belts of flachsanderwurzels. In one case the explosion-like subglacial meltwater outburst combined with the genesis of a sanderwurzel could be observed for a time and is thoroughly discussed. The event is referred to the outburst of a sub- to inglacial meltwater body being under extreme hydrostatic press ures which is combined with the genesis of a new subglacial tunneloutlet as a new flachsander. Often these outbursts led to the destruction of a morainic belt more than 1000 m in width. Presumably the whole event was finished in not more than a few days. In addition to a characteristic pear-shaped form and water-moved stones up to diameters of 1 m the wurzels possess a single "main-channel" with rectangular cross-sections as far as 4 m deep and 50 m wide just as small flat channels resembling fish bones in connection with the main channel. Presumably, they have been active only in the last stage of wurzel formation. With regard to the subglacial tunnel gates long-living L-meltwater outlets are distinguished from short-living K-meltwater outlets. These are always combined with a raised coarse-grained sanderwurzel, but its meltwater discharge is generally decreasing and ceases after some years, whereas the discharge of L-meltwater outlets continues unchanged for long times (except seasonal differences). The material of flachsanders is preponderantly composed of mugearitic and andesitic cobble extending at least for some kilometres from the glacier margin, whereas the hochsanders correspond to medium to coarse sands without clay and without alternations into the direction of flow. The hochsander fans are covered with small braidet channels. Their sedimentary structures are determined by the short time changing of supraglacial meltwater discharge and the upper flow regime combined with the development of antidunes, which rule the channel-flows during the main activity periods in summer. Unlike the subglacial drainage the supraglacial drainage led to only weak effects of erosion on the glacier foreland. So the hochsanders refilled depressions of morainic areas or grew up on older flachsanderwurzels. Whereas all large flachsanders developed in front of approximate stationary glacier margins, the evolution of coherent belts of hochsanders were combined with progressive glacier fronts. On the other hand, there was obviously no evolution at all of large sandar in front of back-melting margins of Kötlujökull. Based on examinations of the glacier surface and on analyses of aerial photographs the different types of sandar are referred to different structures of the glacier snout. Finally chances of surviving of sandar in the proglacial area of Kötlujökull are shortly discussed just as the possibility of an application of the Islandic research results on Pleistocene sandar in northern Germany.

Distribution, genesis and age of the Schlagwasser breccia (Warstein anticline, Rhenish massif)

The name "Schlagwasser breccia" is a synopsis of several debris flows in the Warstein area, which can be derived from the Warstein carbonate platform and the Scharfenberg reef. Though only locally developed, the breccia is important for the understanding of paleogeography and sedimentology in the Eastern Sauerland. Considering this breccia some gravitational-resedimentary slide movements between a high, consisting of reef carbonates, and a basin with flinz beds can be pointed out. From the uppermost Middle Devonian to the lowermost Lower Carboniferous several slides yielded the sedimentary components building up the 30 to 50 m thick polymict breccia. Some breccias were redeposited repeatedly as can be verified by different conodont maxima in single samples. Supplying area was the western part of the Warstein high, from which the slide masses glided off to the East and Southeast, more seldom to the West and Westsouthwest. All conodont zones from the upper Middle Devonian up to the lowermost Carboniferous could be identified in the Schlagwasser breccia. Therefore, an uninterrupted continuous sedimentation must have been prevalent in the supplying area; today this area nearly is denuded of flinz beds and cephalopod limestones. The slide masses spread transgressively to the East up to a substratum consisting of different units as massive limestone, flinz beds and cephalopod limestone; they are overlapped by Hangenberg beds, alum schists and siliceous rocks of the Lower Carboniferous. Parts of the substratum were transported during the progress of the slide masses. Proximal and distal parts of the flow masses can be distinguished by the diameter of the pebbles. Graded bedding and banking structures are marked only rarely. Way of transport was up to 3 km. Differently aged slide masses do not always overlap, but are placed side by side, too. Usually the slide masses do not spread out upon a greater area during sedimentation, but form closely limited debris flows. Synsedimentary fracturing and tilting of the reef platform, epirogenetic movements and seaquakes caused the slides. The entire formation period of the breccia includes about 20 millions of years. The longevity of the events points to solid paleomorphological situations around the eastern margin of the carbonate platform.

Geochemistry of recent sediments from the Indian Ocean

During the International Indian Ocean Expedition (1964/65) sediment cores were taken on six profiles off the western coast of the Indian Subcontinent. These profiles run approximately perpendicular to the coast, from the deep-sea over the continental slope to the continental shelf. Additional samples and cores were taken in a dense pattern in front of the delta of the Indus River. This pattern of sampling covered not only marine sediments, but also river and beach sediments in Pakistan. The marine samples were obtained with piston, gravity and box corers and by a Van Veen grab sampler. The longest piston core is about 5 meters long. 1. Distribution of the elements on the sediment surface The area of maximal carbonate values (aprox. 80-100% CaCO3) essentially coincides with the continental shelf. The highest Sr values were observed largely within this area, but only in the vicinity of the Gulf of Cambay. Mainly the aragonitic coprolites are responsible for those high Sr contents. The Mg contents of the carbonates are comparatively low; surprisingly enough the highest Mg concentrations were also measured in the coprolites. The maximum contents of organic matter (Core) were found along the upper part of the continental slope. They coincide with the highest porosity and water content of the sediments. Frequently the decomposition of organic matter by oxydation is responsible for the measured Corg contents. On the other side the quantity of originally deposited organic material is less important in most cases. The enrichment of the "bauxitophile" elements Fe, Ti, Cr and V in the carbonate- and quartz-free portions of the sediments is essentially due to the influence of coarse terrigenous detritus. For the elements Mn, Ni and Cu (in per cent of the carbonateand quartz-free sediment) a strong enrichment was observed in the deep-sea realm. The strong increase in Mn toward the deep-sea is explained by authigenesis of Mn-Fe-concretions. Mn-nodules form only under oxydizing conditions which obviously are possible only at very low rates of deposition. The Mg, B and, probably also Mn contents in the clay minerals increase with increasing distance from the continent. This can be explained by the higher adsorption of those elements from sea water because of increasing duration of the clay mineral transport. The comparison of median contents of some elements in our deep-sea samples with deep-sea sediments described by TUREKIAN & WEDEPOHL (1961) shows that clear differences in concentration exist only in the case of "bauxitophile" elements Cr and Be. The Cr and Be contents show a clear increase in the Indian Ocean deep-sea samples compared to those described by TUREKIAn & WEDEPOHL (1961) which can obviously be attributed to the enrichment in the lateritic and bauxitic parent rocks. The different behaviour of the elements Fe, Ti and Mn during decomposition of the source rocks, transport to the sea and during oxydizing and reducing conditions in the marine environment can be illustrated by Ti02/Fe and MnO/Fe ratios. The different compositions of the sediments off the Indus Delta and those of the remaining part of the area investigated are characterized by a different distribution of the elements Mn and Ti. 2. Chemical inhomogenities in the sediments Most longer cores show 3 intervals defined by chemical and sedimentological differences. The top-most interval is coarse-grained, the intermedial interval is fine grained and the lower one again somewhat coarser. At the same time it is possible to observe differences from interval to interval in the organogenic and detrital constituents. During the formation of the middle interval different conditions of sedimentation from those active during the previous and subsequent periods have obviously prevailed. Looking more closely at the organogenic constituents it is remarkable that during the formation of the finer interval conditions of a more intensive oxydation have prevailed that was the case before and after: Core decreases, whereas P shows a relative increase. This may be explained by slower sedimentation rate or by a vertical migration of the oxygen rich zone of the sea-water. The modifications of the elements from minerals in detrital portion of the sediments support an explanation ascribing this fact to modifications of the conditions of denudation and transportation which can come about through a climatic change or through tectonic causes. The paleontological investigations have shown (ZOBEL, in press) that in some of the cores the middle stratum of fine sedimentation represents optimal conditions for organic life. This fact suggests also oxydizing conditions during the sedimentation of this interval. In addition to the depositional stratification an oxydation zone characterized by Mn-enrichment can be recognized. The thickness of the oxidation zone decreases towards the coast and thins out along the middle part of the continental slope. At those places, where the oxydation zone is extremely thin, enrichment of Mn has its maximum. This phenomenon can probably be attributed to the migration of Mn taking place in its dissociated form within the sediment under reducing conditions. On the other side this Mn-migration in the sediment does not take place in the deep-sea, where oxydizing conditions prevail. 3. Interstitial waters in the sediments Already at very small core depths, the interstitial waters have undergone a distinct modification compared with the overlying sea water. This distinct modification applies both to total salinity and to the individual ions. As to the beginning of diagenesis the following conclusions can be drawn: a) A strong K-increase occurs already at an early stage. It may be attributable to a diffusion barrier or to an exchange of Mg-ions on the clays. Part of this increase may also originate from the decomposition of K-containing silicates (mica and feldspars). A K-decrease owing to the formation of illite (WEAVER 1967), however, occurs only at much greater sediment depth. b) Because of an organic protective coating, the dissolution of carbonate is delayed in recent organogenic carbonates. At the same time some Ca is probably being adsorbed on clay minerals. Consequently the Ca-content of the interstitial water drops below the Ca-content of the sea water. c) Already at an early stage the Mg adsorption on the clays is completed. The adsorbed Mg is later available for diagenetic mineral formations and transformations.

Chronostratigraphy of sediment core CRP-3 from the Ross Sea, Antarctica

An 823 m thick glaciomarine Cenozoic section sitting unconformably on the Lower Devonian Beacon Supergroup was recovered in CRP-3. This paper reviews the chronostratigraphical constraints for the Cenozoic section. Between 3 and 480.27 mbsf 23 unconformity bounded cycles of sediment were recorded. Each unconformity is thought to represent a hiatus of uncertain duration. Four magnetozones have been recognised from the Cenozoic section. The record is complex with several 'tiny wiggles'' recorded throughout. Biostratigraphical or Sr ages, which could be used to link these magnetozones to the magnetic polarity time scale are restricted to the upper 190 m of sediment. Two diatom datums (Cavitatus jouseanus at 48.9 mbsf and Rhizosolenica antarctica at 68.60 mbsf), together with five Sr-isotope dates derived from molluscan fragments taken from between 10.88 and 190.29 mbsf indicate an early Oligocene (c. 31 Ma) age for this interval. The appearance of a new species of the bivalve ?Adamussium at about 325 mbsf, suggests that the Oligocene age can be extended down to this level. This confirms that the dominantly reversed magnetozone (RI), recorded down to about 340 mbsf, is Chron C12r. The ages imply high sedimentation rates and only minimal time gaps at the sequence boundaries. Below 340 mbsf there are no independent datums to guide the correlation of the magnetozones to the magnetic polarity time scale. However, the absence of in situ dinocysts attributable to Transantarctic Flora, if not a result of environmental control, limits the age of the base of the hole to between c. 33.5 and 35 Ma.

Concentration and isotope composition of sulphur in sediments and pore water at DSDP Leg 70 Holes

Data obtained while investigating the mounds area near the Galapagos Spreading Center demonstrate the direct influence of solutions derived from the interaction of seawater and young oceanic crust on the sedimentary cover. Investigation of metalliferous sediments from the mid-oceanic ridges, the Galapagos mounds, and the FAMOUS-area zone formations have shown that this influence and the resulting products are dependent on composition, temperature, and conditions of solution input. The study of sulfur in upwardly migrating solutions and the interaction of these solutions with sediments is of great interest. Investigations of different types of hydrothermally derived formations (Edmond, et al., 1979; Spiess et al., 1980; Styrt et al., 1981; Rosanova 1976; Grinenko et al., 1978) have shown the significant role of sulfur-bearing minerals in deposits formed from hightemperature solutions. In contrast, the addition of hydrothermal sulfur is negligible in those metalliferous sediments that precipitated as a result of the interaction between the solutions and open seawater (Bonatti et al., 1972, 1976; Gordeev et al., 1979; Migdisov, Bogdanov, et al., 1979). For example, sulfides are absent in clearly oxidized metalliferous sediments from the East Pacific Rise (EPR). Barite sulfur from these sediments is identical with seawater sulfate sulfur in isotope composition (Grinenko et al., 1978). Gurvich and Bogdanov (1977) have suggested that barium from EPR metalliferous sediments results completely from biological activity and from the components of ocean waters. Edmond et al. (1979) report that low-temperature springs from the Galapagos Rift axis contain two types of solutions: those with and those without H2S.

Sociedad y política en argentina (1955-1976) : La 'nueva izquierda' entre la protesta social y la política revolucionaria

El presente proyecto de investigación analiza la relación entre sociedad y política en la Argentina entre 1955 y 1976. Se trata de un período signado por una aguda crisis socio-política, una profunda pérdida de legitimidad de las instituciones y el Estado y en que la acelerada modernización socio-cultural posterior a 1955 se combinó rápidamente con una tendencia a la radicalización política. Uno de los primeros efectos de este proceso fue la recomposición de la izquierda. Del seno de sus partidos "tradicionales" (el Partido Comunista y Socialista) surgieron diversas formaciones de la "nueva izquierda", mientras que rupturas y transformaciones similares se verificaban en sectores nacionalistas, peronistas y cristianos. Estos nuevos actores sociales y políticos solieron orientarse hacia objetivos que proclamaron la "liberación nacional" y el "socialismo" y hacia estrategias revolucionarias. Nuestro trabajo se interesa centralmente en reconstruir los orígenes de las nuevas prácticas y organizaciones surgidas por entonces así como las formas de articulación entre demandas sociales y propuestas políticas, y entre elencos dirigentes y sectores populares. A su vez, examina una multiplicidad de "casos" que formaron parte de este social y políticamente variado campo, sin subsumirlo exclusivamente al accionar de las organizaciones armadas.

Un mapa de representaciones sobre uso/s y usuario/s de drogas ilegales desde la Semiótica de Enunciados

El objetivo del presente trabajo es describir, poner en práctica y evaluar los alcances del método analítico conocido como Semiótica de Enunciados para el análisis de representaciones sociales, a partir de entrevistas realizadas a actores vinculados al fenómeno de las drogas ilegales. En esta oportunidad posibilitó establecer un primer mapa conceptual de cómo diversos actores (legisladores, militantes sociales, usuarios y ex usuarios de drogas, trabajadores estatales en adicciones, miembros de organizaciones civiles) definen uso/s y usuario/s de drogas ilegales, siendo identificadas dos formaciones discursivas que están en tensión. Además deja en evidencia algunas tensiones dentro de cada formación discursiva, así como las correlaciones entre ambas formaciones, y las contradicciones u opacidades en el discurso de los actores

Un mapa de representaciones sobre uso/s y usuario/s de drogas ilegales desde la Semiótica de Enunciados

El objetivo del presente trabajo es describir, poner en práctica y evaluar los alcances del método analítico conocido como Semiótica de Enunciados para el análisis de representaciones sociales, a partir de entrevistas realizadas a actores vinculados al fenómeno de las drogas ilegales. En esta oportunidad posibilitó establecer un primer mapa conceptual de cómo diversos actores (legisladores, militantes sociales, usuarios y ex usuarios de drogas, trabajadores estatales en adicciones, miembros de organizaciones civiles) definen uso/s y usuario/s de drogas ilegales, siendo identificadas dos formaciones discursivas que están en tensión. Además deja en evidencia algunas tensiones dentro de cada formación discursiva, así como las correlaciones entre ambas formaciones, y las contradicciones u opacidades en el discurso de los actores

Un mapa de representaciones sobre uso/s y usuario/s de drogas ilegales desde la Semiótica de Enunciados

El objetivo del presente trabajo es describir, poner en práctica y evaluar los alcances del método analítico conocido como Semiótica de Enunciados para el análisis de representaciones sociales, a partir de entrevistas realizadas a actores vinculados al fenómeno de las drogas ilegales. En esta oportunidad posibilitó establecer un primer mapa conceptual de cómo diversos actores (legisladores, militantes sociales, usuarios y ex usuarios de drogas, trabajadores estatales en adicciones, miembros de organizaciones civiles) definen uso/s y usuario/s de drogas ilegales, siendo identificadas dos formaciones discursivas que están en tensión. Además deja en evidencia algunas tensiones dentro de cada formación discursiva, así como las correlaciones entre ambas formaciones, y las contradicciones u opacidades en el discurso de los actores

Composition of organic matter from samples of massive sulfides, bottom sediments, and seawater collected within the Logachev and Broken Spur hydrothermal fields, Mid-Atlantic Ridge

Lipid components of hydrothermal deposits from the unusual field at 14°45'N MAR and from the typical field at 29°N MAR were studied. For the first time mixed nature of organic matter (OM) from hydrothermal sulfide deposits was established with use of biochemical, gas chromatographic, and molecular methods of studies. In composition of OM lipids of phytoplankton, those of chemosynthesis bacteria and non-biogenic synthesis lipids were determined. Specific conditions of localization of sulfide deposits originated from ''black smokers'' (reducing conditions, absence of free oxygen, presence of reduced sulfur preventing OM from decomposition) let biogenic material, including bacterial one, be preserved in sulfide deposits. The hydrothermal system at 14°45'N MAR is characterized by geological, geochemical and thermodynamic conditions allowing abiogenic synthesis of methane and petroleum hydrocarbons. For sulfide deposits at 29°N and other active hydrothermal fields known at MAR, abiogenic synthesis of hydrocarbons occurs in lower scales.

Sociedad y política en argentina (1955-1976) : La 'nueva izquierda' entre la protesta social y la política revolucionaria

El presente proyecto de investigación analiza la relación entre sociedad y política en la Argentina entre 1955 y 1976. Se trata de un período signado por una aguda crisis socio-política, una profunda pérdida de legitimidad de las instituciones y el Estado y en que la acelerada modernización socio-cultural posterior a 1955 se combinó rápidamente con una tendencia a la radicalización política. Uno de los primeros efectos de este proceso fue la recomposición de la izquierda. Del seno de sus partidos "tradicionales" (el Partido Comunista y Socialista) surgieron diversas formaciones de la "nueva izquierda", mientras que rupturas y transformaciones similares se verificaban en sectores nacionalistas, peronistas y cristianos. Estos nuevos actores sociales y políticos solieron orientarse hacia objetivos que proclamaron la "liberación nacional" y el "socialismo" y hacia estrategias revolucionarias. Nuestro trabajo se interesa centralmente en reconstruir los orígenes de las nuevas prácticas y organizaciones surgidas por entonces así como las formas de articulación entre demandas sociales y propuestas políticas, y entre elencos dirigentes y sectores populares. A su vez, examina una multiplicidad de "casos" que formaron parte de este social y políticamente variado campo, sin subsumirlo exclusivamente al accionar de las organizaciones armadas.

Un mapa de representaciones sobre uso/s y usuario/s de drogas ilegales desde la Semiótica de Enunciados

El objetivo del presente trabajo es describir, poner en práctica y evaluar los alcances del método analítico conocido como Semiótica de Enunciados para el análisis de representaciones sociales, a partir de entrevistas realizadas a actores vinculados al fenómeno de las drogas ilegales. En esta oportunidad posibilitó establecer un primer mapa conceptual de cómo diversos actores (legisladores, militantes sociales, usuarios y ex usuarios de drogas, trabajadores estatales en adicciones, miembros de organizaciones civiles) definen uso/s y usuario/s de drogas ilegales, siendo identificadas dos formaciones discursivas que están en tensión. Además deja en evidencia algunas tensiones dentro de cada formación discursiva, así como las correlaciones entre ambas formaciones, y las contradicciones u opacidades en el discurso de los actores

Sociedad y política en argentina (1955-1976) : La 'nueva izquierda' entre la protesta social y la política revolucionaria

El presente proyecto de investigación analiza la relación entre sociedad y política en la Argentina entre 1955 y 1976. Se trata de un período signado por una aguda crisis socio-política, una profunda pérdida de legitimidad de las instituciones y el Estado y en que la acelerada modernización socio-cultural posterior a 1955 se combinó rápidamente con una tendencia a la radicalización política. Uno de los primeros efectos de este proceso fue la recomposición de la izquierda. Del seno de sus partidos "tradicionales" (el Partido Comunista y Socialista) surgieron diversas formaciones de la "nueva izquierda", mientras que rupturas y transformaciones similares se verificaban en sectores nacionalistas, peronistas y cristianos. Estos nuevos actores sociales y políticos solieron orientarse hacia objetivos que proclamaron la "liberación nacional" y el "socialismo" y hacia estrategias revolucionarias. Nuestro trabajo se interesa centralmente en reconstruir los orígenes de las nuevas prácticas y organizaciones surgidas por entonces así como las formas de articulación entre demandas sociales y propuestas políticas, y entre elencos dirigentes y sectores populares. A su vez, examina una multiplicidad de "casos" que formaron parte de este social y políticamente variado campo, sin subsumirlo exclusivamente al accionar de las organizaciones armadas.