Cenozoic planktonic foraminifera of the Falkland Plateau and Argentine Basin

Sites 511 and 512 (Falkland Plateau) and 513 (Argentine Basin) penetrated calcareous-siliceous oozes of the middle and upper Eocene and lower Oligocene with rather numerous planktonic foraminifers. Upper Oligocene, Miocene, Pliocene, and Quaternary sections are composed mostly of siliceous sediments (Sites 511-514) where planktonic foraminifers are rare or absent. High-latitude planktonic foraminifers of the Austral Province are characterized by impoverished assemblages - only representatives of Globigerina, Globigerinita, Globorotaloides, and Globorotalia with a rounded peripheral margin are found. In the Paleogene, these species are supplemented, in lesser amounts, by representatives of Globigerapsis, Acarinina, Pseudogloboquadrina, Pseudohastigerina, and Chiloguembelina. Assemblages of planktonic foraminifers have low stratigraphic resolution, especially in the upper Oligocene-Quaternary. This reflects the generally deteriorating Cenozoic climate, which evinced a sharp change in the upper Oligocene that is connected with initiation of the circum-Antarctic current near the Paleogene/Neogene boundary. Comparison of Paleogene and Neogene planktonic foraminifers of the South Atlantic (Falkland Plateau, Argentine Basin, 46-51°S) and the North Atlantic (Rockall Plateau, 55-56°N) indicates that the South Atlantic climate was much colder than that of the same latitudes of the North Atlantic. Paleogene oozes of the Falkland Plateau rest unconf ormably on Maestrichtian sediments and in their turn are overlain unconformably by Neogene-Quaternary oozes. Cenozoic sections are stratigraphically discontinuous: periods of intensive biogenic sedimentation resulting in a thick succession of sediments alternated with periods of nondeposition and strong erosion that resulted in hiatuses and unconformities. In the Argentine Basin, Oligocene calcareous-siliceous oozes rest on basalts of the oceanic basement; they are replaced upward in the section by Neogene-Quaternary siliceous oozes with some hiatuses. Planktonic foraminifers here clearly demonstrate the processes of oceanic subsidence and CCD fluctuations as well as Polar Front migrations during Cenozoic time. Fifty species of planktonic foraminifers are discussed and illustrated.

Annual layer thicknesses and age-depth (oldest estimate) of Derwael Ice Rise (IC12), Dronning Maud Land, East Antarctica

A 120 m-long ice core was drilled in 2012 on the Derwael Ice Rise, coastal Dronning Maud Land, East Antarctica. Water stable isotopes (d18O and dD) stratigraphy is supplemented by discontinuous major ion profiles and continuous electrical conductivity measurements. The base of the ice core is dated to AD 1759 ± 16, providing a climate proxy for the past ~250 years. This data set presents the core's annual layer thickness history in meters water equivalent for the oldest age-depth estimate before correction for the influence of ice deformation.

Asalariados rurales en el Valle de Uco (Mendoza, Argentina)

El objetivo de este artículo es analizar la inserción laboral de los trabajadores agrícolas asalariados en el Valle de Uco, provincia de Mendoza. Partimos de entender que las características del mercado de trabajo agrícola condicionan las inserciones laborales generando prácticas sociales ocupacionales que se expresan en disposiciones, orientaciones y estrategias de estos trabajadores. Estos trabajadores se caracterizan por una inserción laboral precaria y/o inestable y la percepción de ingresos insuficientes y discontinuos, a lo que se suman las frecuentes condiciones de vulnerabilidad social de sus hogares de pertenencia. El artículo contiene una descripción de la esfera laboral en tanto campo social en que se desempeñan los trabajadores agrícolas en el Valle de Uco. Luego analizamos algunos elementos vinculados a la socialización en el trabajo, aspecto importante para comprender las relaciones sociales que fundamentan la constitución del mercado de trabajo agrícola y la construcción de las "disposiciones" de los trabajadores. En el siguiente punto describimos y analizamos algunos elementos que orientan la inserción laboral de los trabajadores agrícolas conformando sus estrategias laborales. Finalmente, analizamos la mediación del hogar en la inserción laboral de los miembros.

Homero y Platón : Dos paradigmas de la educación corporal

El presente trabajo constituye una especie de reseña de la tesis doctoral del mismo título que demuestra que el cuerpo de las prácticas no es físico, unitario, constante y susceptible de conciencia de sí sino, por el contrario, insubstancial, fragmentado, inconstante e imposibilitado de autopercibirse como unidad: fragmentos y acciones unificados por el significante y no por la percepción. Para obtener estas conclusiones, el trabajo revisa las prácticas corporales de la Grecia clásica y helénica y las que se sucedieron del Renacimiento a la actualidad; repasa el periplo del pensamiento occidental de la multiplicidad discontinua a la unidad y la constancia; analiza el cuerpo en Homero y en Platón; y las relaciones que la fragmentación y la unidad del cuerpo guardan con la oralidad primaria y secundaria, y con la escritura, revelando que fue el gesto socrático que identificó el alma con un "mundo interior" el que otorgó unidad al cuerpo, gesto precedido por el advenimiento del Uno y reforzado por la identificación platónica del Uno con el Bien. En este marco, se opone el cuerpo homérico, fragmentado, al cuerpo unificado por Platón, no porque aquél sea más natural que éste o éste más artificial que aquél, o uno más genuino o verdadero que el otro, sino a partir del análisis de la estructura de la oralidad y la escritura

Isotopic composition of terrestrial plant waxes (dD and d13C of n-alkanes) of sediment core SO188_342 from the Northern Bay of Bengal for the last 18 ka

The Indian Summer Monsoon (ISM) is a major global climatic phenomenon. Long-term precipitation proxy records of the ISM, however, are often fragmented and discontinuous, impeding an estimation of the magnitude of precipitation variability from the Last Glacial to the present. To improve our understanding of past ISM variability, we provide a continuous reconstructed record of precipitation and continental vegetation changes from the lower Ganges-Brahmaputra-Meghna catchment and the Indo-Burman ranges over the last 18,000 years (18 ka). The records derive from a marine sediment core from the northern Bay of Bengal (NBoB), and are complemented by numerical model results of spatial moisture transport and precipitation distribution over the Bengal region. The isotopic composition of terrestrial plant waxes (dD and d13C of n-alkanes) are compared to results from an isotope-enabled general atmospheric circulation model (IsoCAM) for selected time slices (pre-industrial, mid-Holocene and Heinrich Stadial 1). Comparison of proxy and model results indicate that past changes in the dD of precipitation and plant waxes were mainly driven by the amount effect, and strongly influenced by ISM rainfall. Maximum precipitation is detected for the Early Holocene Climatic Optimum (EHCO; 10.5-6 ka BP), whereas minimum precipitation occurred during the Heinrich Stadial 1 (HS1; 16.9-15.4 ka BP). The IsoCAM model results support the hypothesis of a constant moisture source (i.e. the NBoB) throughout the study period. Relative to the pre-industrial period the model reconstructions show 20% more rain during the mid-Holocene (6 ka BP) and 20% less rain during the Heinrich Stadial 1 (HS1), respectively. A shift from C4-plant dominated ecosystems during the glacial to subsequent C3/C4-mixed ones during the interglacial took place. Vegetation changes were predominantly driven by precipitation variability, as evidenced by the significant correlation between the dD and d13C alkane records. When compared to other records across the ISM domain, precipitation and vegetation changes inferred from our records and the numerical model results provide evidence for a coherent regional variability of the ISM from the Last Glacial to the present.

Asalariados rurales en el Valle de Uco (Mendoza, Argentina)

El objetivo de este artículo es analizar la inserción laboral de los trabajadores agrícolas asalariados en el Valle de Uco, provincia de Mendoza. Partimos de entender que las características del mercado de trabajo agrícola condicionan las inserciones laborales generando prácticas sociales ocupacionales que se expresan en disposiciones, orientaciones y estrategias de estos trabajadores. Estos trabajadores se caracterizan por una inserción laboral precaria y/o inestable y la percepción de ingresos insuficientes y discontinuos, a lo que se suman las frecuentes condiciones de vulnerabilidad social de sus hogares de pertenencia. El artículo contiene una descripción de la esfera laboral en tanto campo social en que se desempeñan los trabajadores agrícolas en el Valle de Uco. Luego analizamos algunos elementos vinculados a la socialización en el trabajo, aspecto importante para comprender las relaciones sociales que fundamentan la constitución del mercado de trabajo agrícola y la construcción de las "disposiciones" de los trabajadores. En el siguiente punto describimos y analizamos algunos elementos que orientan la inserción laboral de los trabajadores agrícolas conformando sus estrategias laborales. Finalmente, analizamos la mediación del hogar en la inserción laboral de los miembros.

Homero y Platón : Dos paradigmas de la educación corporal

El presente trabajo constituye una especie de reseña de la tesis doctoral del mismo título que demuestra que el cuerpo de las prácticas no es físico, unitario, constante y susceptible de conciencia de sí sino, por el contrario, insubstancial, fragmentado, inconstante e imposibilitado de autopercibirse como unidad: fragmentos y acciones unificados por el significante y no por la percepción. Para obtener estas conclusiones, el trabajo revisa las prácticas corporales de la Grecia clásica y helénica y las que se sucedieron del Renacimiento a la actualidad; repasa el periplo del pensamiento occidental de la multiplicidad discontinua a la unidad y la constancia; analiza el cuerpo en Homero y en Platón; y las relaciones que la fragmentación y la unidad del cuerpo guardan con la oralidad primaria y secundaria, y con la escritura, revelando que fue el gesto socrático que identificó el alma con un "mundo interior" el que otorgó unidad al cuerpo, gesto precedido por el advenimiento del Uno y reforzado por la identificación platónica del Uno con el Bien. En este marco, se opone el cuerpo homérico, fragmentado, al cuerpo unificado por Platón, no porque aquél sea más natural que éste o éste más artificial que aquél, o uno más genuino o verdadero que el otro, sino a partir del análisis de la estructura de la oralidad y la escritura

Chemistry and accumulation rates of Jurassic to early Cretaceous sediments from the central equatorial Pacific

Sedimentation in the central Pacific during the Jurassic and Early Cretaceous was dominated by abundant biogenic silica. A synthesis of the stratigraphy, lithology, petrology, and geochemistry of the radiolarites in Sites 801 and 800 documents the sedimentation processes and trends in the equatorial central Pacific from the Middle Jurassic through the Early Cretaceous. Paleolatitude and paleodepth reconstructions enable comparisons with previous DSDP sites and identification of the general patterns of sedimentation over a wide region of the Pacific. Clayey radiolarites dominated sedimentation on Pacific oceanic crust within tropical paleolatitudes from at least the latest Bathonian through Tithonian. Radiolarian productivity rose to a peak within 5° of the paleoequator, where accumulation rates of biogenic silica exceeded 1000 g/cm**2/m.y. Wavy-bedded radiolarian cherts developed in the upper Tithonian at Site 801 coinciding with the proximity of this site to the paleoequator. Ribbon-bedding of some radiolarian cherts exposed on Pacific margins may have formed from silicification of radiolarite deposited near the equatorial high-productivity zone where radiolarian/clay ratios were high. Silicification processes in sediments extensively mixed by bioturbation or enriched in clay or carbonate generally resulted in discontinuous bands or nodules of porcellanite or chert, e.g., a "knobby" radiolarite. Ribbon-bedded cherts require primary alternations of radiolarian-rich and clay-rich layers as an initial structural template, coupled with abundant biogenic silica in both layers. During diagenesis, migration of silica from clay-rich layers leaves radiolarian "ghosts" or voids, and the precipitation in adjacent radiolarite layers results in silicification of the inter-radiolarian matrix and infilling of radiolarian tests. Alternations of claystone and clay-rich radiolarian grainstone were deposited during the Callovian at Site 801 and during the Berriasian-Valanginian at Site 800, but did not silicify to form bedded chert. Carbonate was not preserved on the Pacific oceanic floor or spreading ridges during the Jurassic, perhaps due to an elevated level of dissolved carbon dioxide. During the Berriasian through Hauterivian, the carbonate compensation depth (CCD) descended to approximately 3500 m, permitting the accumulation of siliceous limestones at near-ridge sites. Carbonate accumulation rates exceeded 1500 g/cm**2/m.y. at sites above the CCD, yet there is no evidence of an equatorial carbonate bulge during the Early Cretaceous. In the Barremian and Aptian, the CCD rose, coincident with the onset of mid-plate volcanic activity. Abundance of Fe and Mn and the associated formation of authigenic Fe-smectite clays was a function of proximity to the spreading ridges, with secondary enrichments occurring during episodes of spreading-center reorganizations. Callovian radiolarite at Site 801 is anomalously depleted in Mn, which resulted either from inhibited precipitation of Mn-oxides by lower pH of interstitial waters induced by high dissolved oceanic CO2 levels or from diagenetic mobilization of Mn. Influx of terrigenous (eolian) clay apparently changed with paleolatitude and geological age. Cyclic variations in productivity of radiolarians and of nannofossils and in the influx of terrigenous clay are attributed to Milankovitch climatic cycles of precession (20,000 yr) and eccentricity (100,000 yr). Diagenetic redistribution of biogenic silica and carbonate enhanced the expression of this cyclic sedimentation. Jurassic and Lower Cretaceous sediments were deposited under oxygenated bottom-water conditions at all depths, accompanied by bioturbation and pervasive oxidation of organic carbon and metals. Despite the more "equable" climate conditions of the Mesozoic, the super-ocean of the Pacific experienced adequate deep-water circulation to prevent stagnation. Efficient nutrient recycling may have been a factor in the abundance of radiolarians in this ocean basin.

Age determination and color reflectance of ODP Hole 165-1002D

Attempts to place Palaeolithic finds within a precise climatic framework are complicated by both uncertainty over the radiocarbon calibration beyond about 21,500 14C years bp (Reimer et al., 2004) and the absence of a master calendar chronology for climate events from reference archives such as Greenland ice cores or speleothems (Svensson et al., 2006, doi:10.1016/j.quascirev.2006.08.003). Here we present an alternative approach, in which 14C dates of interest are mapped directly onto the palaeoclimate record of the Cariaco Basin by means of its 14C series (Hughen et al., 2004, doi:10.1126/science.1090300), circumventing calendar age model and correlation uncertainties, and placing dated events in the millennial-scale climate context of the last glacial period. This is applied to different sets of dates from levels with Mousterian artefacts, presumably produced by late Neanderthals, from Gorham's Cave in Gibraltar: first, generally accepted estimates of about 32,000 14C years bp for the uppermost Mousterian levels (Pettitt and Bailey, 2000; Bronk Ramsey et al., 2002, doi:10.1111/1475-4754.00040); second, a possible extended Middle Palaeolithic occupation until about 28,000 14C years bp (Finlayson et al., 2006, doi:10.1038/nature05195); and third, more contentious evidence for persistence until about 24,000 14C years bp (Finlayson et al., 2006, doi:10.1038/nature05195). This study shows that the three sets translate to different scenarios on the role of climate in Neanderthal extinction. The first two correspond to intervals of general climatic instability between stadials and interstadials that characterized most of the Middle Pleniglacial and are not coeval with Heinrich Events. In contrast, if accepted, the youngest date indicates that late Neanderthals may have persisted up to the onset of a major environmental shift, which included an expansion in global ice volume and an increased latitudinal temperature gradient. More generally, our radiocarbon climatostratigraphic approach can be applied to any 'snapshot' date from discontinuous records in a variety of deposits and can become a powerful tool in evaluating the climatic signature of critical intervals in Late Pleistocene human evolution.

Homero y Platón : Dos paradigmas de la educación corporal

El presente trabajo constituye una especie de reseña de la tesis doctoral del mismo título que demuestra que el cuerpo de las prácticas no es físico, unitario, constante y susceptible de conciencia de sí sino, por el contrario, insubstancial, fragmentado, inconstante e imposibilitado de autopercibirse como unidad: fragmentos y acciones unificados por el significante y no por la percepción. Para obtener estas conclusiones, el trabajo revisa las prácticas corporales de la Grecia clásica y helénica y las que se sucedieron del Renacimiento a la actualidad; repasa el periplo del pensamiento occidental de la multiplicidad discontinua a la unidad y la constancia; analiza el cuerpo en Homero y en Platón; y las relaciones que la fragmentación y la unidad del cuerpo guardan con la oralidad primaria y secundaria, y con la escritura, revelando que fue el gesto socrático que identificó el alma con un "mundo interior" el que otorgó unidad al cuerpo, gesto precedido por el advenimiento del Uno y reforzado por la identificación platónica del Uno con el Bien. En este marco, se opone el cuerpo homérico, fragmentado, al cuerpo unificado por Platón, no porque aquél sea más natural que éste o éste más artificial que aquél, o uno más genuino o verdadero que el otro, sino a partir del análisis de la estructura de la oralidad y la escritura

Asalariados rurales en el Valle de Uco (Mendoza, Argentina)

El objetivo de este artículo es analizar la inserción laboral de los trabajadores agrícolas asalariados en el Valle de Uco, provincia de Mendoza. Partimos de entender que las características del mercado de trabajo agrícola condicionan las inserciones laborales generando prácticas sociales ocupacionales que se expresan en disposiciones, orientaciones y estrategias de estos trabajadores. Estos trabajadores se caracterizan por una inserción laboral precaria y/o inestable y la percepción de ingresos insuficientes y discontinuos, a lo que se suman las frecuentes condiciones de vulnerabilidad social de sus hogares de pertenencia. El artículo contiene una descripción de la esfera laboral en tanto campo social en que se desempeñan los trabajadores agrícolas en el Valle de Uco. Luego analizamos algunos elementos vinculados a la socialización en el trabajo, aspecto importante para comprender las relaciones sociales que fundamentan la constitución del mercado de trabajo agrícola y la construcción de las "disposiciones" de los trabajadores. En el siguiente punto describimos y analizamos algunos elementos que orientan la inserción laboral de los trabajadores agrícolas conformando sus estrategias laborales. Finalmente, analizamos la mediación del hogar en la inserción laboral de los miembros.

Mineralogy, and composition of turbidites and background samples at ODP Sites 166-1003 and 166-1007

The lower slope and toe-of-slope sediments of the western flank of the Great Bahama Bank (Sites 1003 and 1007) are characterized by an intercalation of turbidites and periplatform ooze. In general, turbidites form up to 12% of the total mass of the sedimentary column. Based primarily on data from the Bahamas, it has been postulated that steep-sided carbonate platforms shed most of their sediments into the basin during sea-level highstands when the platforms are flooded. This highstand shedding is assumed to be less pronounced along platforms with a ramp-like depositional profile where sediment production is not restricted to sea-level highstand. Miocene to Pliocene sediments recovered in five drill holes during Leg 166 at the western margin of the Great Bahama Bank reveal that turbidite distribution follows a complex pattern that is dependent on several factors such as sedimentation rates, sea-level changes, and slope morphology. To identify the depositional sequences in the cores, the depths of seismic-sequence boundaries were used. The distribution of turbidites within sedimentary sequences varies strongly. Generally, turbidites are clustered at the upper and/or lower portions of the sequences indicating deposition of carbonate turbidites during both highstand and lowstand of sea level. Analyses of the Miocene turbidites show that (1) during high sea level, 60% of all turbidites were deposited at Site 1003 (309 out of 518 turbidites), while during low sea level, two thirds of all turbidites were deposited at Site 1007 (332 out of 486 turbidites); (2) the average thickness of highstand turbidites is 1.5 times higher than the average thickness of lowstand turbidites; and (3) the turbidites display slight differences in composition and sorting. In general, highstand turbidites are less sorted and contain an abundant amount of shallow-water constituents such as green algae, red algae, shallow-water benthic foraminifers (miliolids), and intraclasts. The lowstand turbidites are better sorted and contain abundant planktonic foraminifers and micrite. To complicate matters, highstand and lowstand turbidites seem to be deposited at different locations on the slope. At the lower slope (Site 1003), more turbidites were deposited during highstands, while at the toe of the slope, turbidites were dominantly deposited during sea-level lowstands. The result is a slope section with laterally discontinuous turbidite lenses within periplatform ooze, which is controlled by the interplay of sea-level changes, sediment production, and platform morphology.

Mass-accumulation rates for the non-authigenic, inorganic, crystalline, eolian component of sediments recovered at DSDP Sites 62-464 to 62-466

The mass-accumulation rate (MAR) of the non-authigenic, inorganic, crystalline component of deep-sea sediments from the Pacific aseismic rises apparently reflects influx of eolian sediment. The eolian sediment usually is dominated by volcanic material, except during glacial times. Sediments from Hess Rise provide a discontinuous record of eolian MARs. During Albian to Cenomanian time, the influx of volcanic material was fairly high (0.35-0.6 g/cm**2/10**3 yr), recording the latest stages of the Albian volcanism that formed Hess Rise. From the Campanian through the Paleocene, influx of eolian sediment was low, averaging 0.03 g/cm**2/10**3 yr. None of the four Hess Rise drill sites show evidence of the Late Cretaceous volcanic episode recorded at many sites now in the equatorial to subtropical Pacific. Pliocene to Pleistocene samples record a peak in volcanic influx about 4 to 5 m.y. ago, which has been well documented elsewhere. The several-fold increase in eolian accumulation rates elsewhere which are correlated with the onset of severe northernhemisphere glaciation 2.5 m.y. ago is not obvious in the Hess Rise data.

Abrupt shifts of the Sahara-Sahel boundary during Heinrich stadials demonstrated on a sediment core transect

Relict dune fields that are found as far south as 14° N in the modern-day African Sahel are testament to equatorward expansions of the Sahara desert during the Late Pleistocene. However, the discontinuous nature of dune records means that abrupt millennial-timescale climate events are not always resolved. High-resolution marine core studies have identified Heinrich stadials as the dustiest periods of the last glacial in West Africa although the spatial evolution of dust export on millennial timescales has so far not been investigated. We use the major-element composition of four high-resolution marine sediment cores to reconstruct the spatial extent of Saharan-dust versus river-sediment input to the continental margin from West Africa over the last 60 ka. This allows us to map the position of the sediment composition corresponding to the Sahara-Sahel boundary. Our records indicate that the Sahara-Sahel boundary reached its most southerly position (13° N) during Heinrich stadials and hence suggest that these were the periods when the sand dunes formed at 14° N on the continent. Heinrich stadials are associated with cold North Atlantic sea surface temperatures which appear to have triggered abrupt increases of aridity and wind strength in the Sahel. Our study illustrates the influence of the Atlantic meridional overturning circulation on the position of the Sahara-Sahel boundary and on global atmospheric dust loading.

Description and chemical composition of ferromanganese nodules from Station 123, Oneida Lake, New York

226Ra is used to document the growth histories of six manganese nodules from Oneida Lake, New York. Detailed sectioning and analysis reveal that there are discontinuous gradients in 226Ra content in these samples. These gradients result from periods of rapid growth (>1 mm/100 years) separated by periods of no growth of erosion. Although the 226Ra 'age' of the nodules approximates the age of Oneida Lake, the nodules are not sediment-covered because they occur only in areas of the lake where fine-grained sediments are not accumulating.