Late Quaternary planktonic foraminifera of ODP Hole 175-1087A

Planktonic foraminiferal assemblages from the upper Pleistocene part of Hole 1087A (0 to 12.1 meters below seafloor) are investigated to assess the role of global and local climate changes on surface circulation in the southern Benguela region. The benthic stable isotope record indicates that the studied interval is representative of the last four climatic cycles, that is, down to marine isotope Stage (MIS) 12. The species assemblages bear a clear transitional to subpolar character, with Neogloboquadrina pachyderma (d), Globorotalia inflata, and Globigerina bulloides, in order of decreasing abundance, as the dominant taxa. This species association presently characterizes the mixing domain of old upwelled and open ocean waters, seaward of the Benguela upwelling cells. Abundance variation of the dominant foraminiferal species roughly follows a glacial-interglacial pattern down to MIS 8, suggesting an alternation of upwelling strength and associated seaward extension of the belt of upwelled water as a response to global climate changes. This pattern is interrupted from ~250 ka down to MIS 12, where the phase relationship with global climate is ill defined and might be interpreted as a local response of the southern Benguela region to the mid-Brunhes event. Of particular interest is a single pulse of newly upwelled waters at the location of Site 1087 during early MIS 9 as indicated by a peak abundance of sinistral N. pachyderma (s). Variable input of warm, salty Indian Ocean thermocline waters into the southeast Atlantic, a key component of the Atlantic heat conveyor, is indicated by abundance changes of the tropical taxon Globorotalia menardii. From this tracer, we suggest that interocean exchange was hardly interrupted throughout the last 460 k.y., but was most effective at glacial terminations, particularly during Terminations I and II, as well as during the upper part of MIS 12. This maximum input of Indian Ocean waters around the southern tip of Africa is associated with the reseeding of G. menardii in the tropical Atlantic.

In memoriam : Alan Deyermond y la oralidad en la literatura medieval hispánica

La figura de Alan Deyermond fue esencial para desarrollar los congresos de Lyra Minima. La oralidad, la autoría femenina y la interacción entre lírica culta y popular han sido temas caros a su obra. Uno de sus conceptos más acertado es la de textos transicionales referidos a los que fueron producidos durante el periodo final de la Edad Media y comienzos del Renacimiento. La relación oralidad - cultura-escrita durante esa época aparece como una transformación, como una superación y como una simbiosis. A Deyermond le resulta probable que la tradición poética popular y oral comenzara canciones de mujer llena de símbolos naturales e imágenes elementales

Asegurar la 'defensa y custodia' de las campañas : Vaquerías y diplomacia interétnica en las sierras pampeanas durante la primera mitad del siglo XVIII

El trabajo analiza un hecho que puede ser considerado el primer contacto diplomático oficial entre las autoridades de Buenos Aires y los indígenas de la pampa: el nombramiento, en febrero de 1717, de dos caciques que habitaban las serranías como Guardas Mayores para la "defensa y custodia" de las campañas. Para entender el motivo de este hecho sin precedentes se analizan los crecientes conflictos entre hispanocriollos por el acceso al ganado cimarrón y los intensos contactos en las serranías durante las décadas de transición del siglo XVII al XVIII donde convergían indígenas de diferentes regiones -incluyendo el área cordillerana- e hispanocriollos de diferentes jurisdicciones, todos ellos atraídos por la abundancia de ganado cimarrón. Finalmente, el trabajo ofrece una interpretación del nombramiento de los caciques en 1717 en función tanto de los intereses porteños como de los intereses indígenas.

Questões sobre Classes, Dominação e Conflitos Sociais na Alta Idade Média

Except for a History that is mobilized, nowadays, much more by the supposedly continuities than the changes, the periods of major transitions continue to demand interpretative effort from specialists. It is long the list of those who have been dedicated to the transitional problem between the Antiquity and the Middle Ages, focused on a period of poor and unequally distributed sources, trying to shed light and establish various interpretative means for this phenomenon. Albeit having overcome some of the catastrophic perspectives hindering the pioneer analyses within this context, the current approaches have also eliminated the recognition of both the contradictory manifestations and the social struggles acting as central and fundamental engines of the social transformations within the discussed context. When supported by an adequate theoretical background, documents from the period lead us to a process resulting from contradictions and a scenario of actions and reactions that eventually materialized the conflicts and moved History forward. The transition from the Antiquity to the Middle Ages was encompassed by diverse social antagonist manifestations, which allows us to consider that the arena of disputes were, therefore, that of the society itself.

Sedimentology, foraminiferal assemblage, and isotope record of the Agulhas Bank region

The Agulhas Bank region, south of Africa, is an oceanographically important and complex area. The leakage of warm saline Indian Ocean water into the South Atlantic around the southern tip of Africa is a crucial factor in the global thermohaline circulation. Foraminiferal assemblage, stable isotope and sedimentological data from the top 10 m of core MD962080, recovered from the western Agulhas Bank Slope, are used to indicate changes in water mass circulation in the southeastern South Atlantic for the last 450 kyr. Sedimentological and planktonic foraminiferal data give clear signals of cold water intrusions. The benthic stable isotope record provides the stratigraphic framework and indicates that the last four climatic cycles are represented (i.e. down to marine isotope stage (MIS) 12). The planktonic foraminiferal assemblages bear a clear transitional to subantarctic character with Globorotalia inflata and Neogloboquadrina pachyderma (dextral) being the dominant taxa. Input of cold, subantarctic waters into the region by means of leakage through the Subtropical Convergence, as part of Agulhas ring shedding, and a general cooling of surface waters is suggested by increased occurrence of the subantarctic assemblage during glacial periods. Variable input of Indian Ocean waters via the Agulhas Current is indicated by the presence of tropical/subtropical planktonic foraminiferal species Globoquadrina dutertrei, Globigerinoides ruber (alba) and Globorotalia menardii with maximum leakage occurring at glacial terminations. The continuous presence of G. menardii throughout the core suggests that the exchange of water from the South Indian Ocean to the South Atlantic Ocean was never entirely obstructed in the last 450 kyr. The benthic carbon isotope record and sediment textural data reflect a change in bottom water masses over the core location from North Atlantic Deep Water to Upper Southern Component Water. Planktonic foraminiferal assemblages and sediment composition indicate a profound change in surface water conditions over the core site approximately 200-250 kyr BP, during MIS 7, from mixed subantarctic and transitional water masses to overall warmer surface water conditions.

In memoriam : Alan Deyermond y la oralidad en la literatura medieval hispánica

La figura de Alan Deyermond fue esencial para desarrollar los congresos de Lyra Minima. La oralidad, la autoría femenina y la interacción entre lírica culta y popular han sido temas caros a su obra. Uno de sus conceptos más acertado es la de textos transicionales referidos a los que fueron producidos durante el periodo final de la Edad Media y comienzos del Renacimiento. La relación oralidad - cultura-escrita durante esa época aparece como una transformación, como una superación y como una simbiosis. A Deyermond le resulta probable que la tradición poética popular y oral comenzara canciones de mujer llena de símbolos naturales e imágenes elementales

Asegurar la 'defensa y custodia' de las campañas : Vaquerías y diplomacia interétnica en las sierras pampeanas durante la primera mitad del siglo XVIII

El trabajo analiza un hecho que puede ser considerado el primer contacto diplomático oficial entre las autoridades de Buenos Aires y los indígenas de la pampa: el nombramiento, en febrero de 1717, de dos caciques que habitaban las serranías como Guardas Mayores para la "defensa y custodia" de las campañas. Para entender el motivo de este hecho sin precedentes se analizan los crecientes conflictos entre hispanocriollos por el acceso al ganado cimarrón y los intensos contactos en las serranías durante las décadas de transición del siglo XVII al XVIII donde convergían indígenas de diferentes regiones -incluyendo el área cordillerana- e hispanocriollos de diferentes jurisdicciones, todos ellos atraídos por la abundancia de ganado cimarrón. Finalmente, el trabajo ofrece una interpretación del nombramiento de los caciques en 1717 en función tanto de los intereses porteños como de los intereses indígenas.

Questões sobre Classes, Dominação e Conflitos Sociais na Alta Idade Média

Except for a History that is mobilized, nowadays, much more by the supposedly continuities than the changes, the periods of major transitions continue to demand interpretative effort from specialists. It is long the list of those who have been dedicated to the transitional problem between the Antiquity and the Middle Ages, focused on a period of poor and unequally distributed sources, trying to shed light and establish various interpretative means for this phenomenon. Albeit having overcome some of the catastrophic perspectives hindering the pioneer analyses within this context, the current approaches have also eliminated the recognition of both the contradictory manifestations and the social struggles acting as central and fundamental engines of the social transformations within the discussed context. When supported by an adequate theoretical background, documents from the period lead us to a process resulting from contradictions and a scenario of actions and reactions that eventually materialized the conflicts and moved History forward. The transition from the Antiquity to the Middle Ages was encompassed by diverse social antagonist manifestations, which allows us to consider that the arena of disputes were, therefore, that of the society itself.

Asegurar la 'defensa y custodia' de las campañas : Vaquerías y diplomacia interétnica en las sierras pampeanas durante la primera mitad del siglo XVIII

El trabajo analiza un hecho que puede ser considerado el primer contacto diplomático oficial entre las autoridades de Buenos Aires y los indígenas de la pampa: el nombramiento, en febrero de 1717, de dos caciques que habitaban las serranías como Guardas Mayores para la "defensa y custodia" de las campañas. Para entender el motivo de este hecho sin precedentes se analizan los crecientes conflictos entre hispanocriollos por el acceso al ganado cimarrón y los intensos contactos en las serranías durante las décadas de transición del siglo XVII al XVIII donde convergían indígenas de diferentes regiones -incluyendo el área cordillerana- e hispanocriollos de diferentes jurisdicciones, todos ellos atraídos por la abundancia de ganado cimarrón. Finalmente, el trabajo ofrece una interpretación del nombramiento de los caciques en 1717 en función tanto de los intereses porteños como de los intereses indígenas.

Questões sobre Classes, Dominação e Conflitos Sociais na Alta Idade Média

Except for a History that is mobilized, nowadays, much more by the supposedly continuities than the changes, the periods of major transitions continue to demand interpretative effort from specialists. It is long the list of those who have been dedicated to the transitional problem between the Antiquity and the Middle Ages, focused on a period of poor and unequally distributed sources, trying to shed light and establish various interpretative means for this phenomenon. Albeit having overcome some of the catastrophic perspectives hindering the pioneer analyses within this context, the current approaches have also eliminated the recognition of both the contradictory manifestations and the social struggles acting as central and fundamental engines of the social transformations within the discussed context. When supported by an adequate theoretical background, documents from the period lead us to a process resulting from contradictions and a scenario of actions and reactions that eventually materialized the conflicts and moved History forward. The transition from the Antiquity to the Middle Ages was encompassed by diverse social antagonist manifestations, which allows us to consider that the arena of disputes were, therefore, that of the society itself.

Composition of carbonaceous sediments from the Late Jurassic Volgian Basin of the East European Platform (Kostroma Region, Russia)

Lithological, geochemical, stratigraphic, and paleoecological features of carbonaceous sediments in the Late Jurassic Volgian Basin of the East European Platform (Kostroma Region) are considered. The shale-bearing sequence studied is characterized by greater sedimentological completeness as compared with its stratotype sections in the Middle Volga region (Gorodishche, Kashpir). Stratigraphic position and stratigraphy of the shale-bearing sequence, as well as distribution of biota in different sedimentation settings are specified. It is shown that Volgian sediments show distinct cyclic structure. The lower and upper elements of cyclites consist of high-carbonaceous shales and clayey-calcareous sediments, respectively, separated by transitional varieties. Bioturbation structures in different rocks are discussed. Microcomponent composition and pyrolytic parameters of organic matter, as well as distribution of chemical elements in lithologically variable sediments are analyzed. Possible reasons responsible for appearance of cyclicity and accumulation of organic-rich sediments are discussed.

Composition of minerals from peridotides at the Mid-Atlantic Ridge, 13°N

Peridotites (diopside-bearing harzburgites) found at 13°N of the Mid-Atlantic Ridge fall into two compositional groups. Peridotites P1 are plagioclase-free rocks with minerals of uniform composition and Ca-pyroxene strongly depleted in highly incompatible elements. Peridotites P2 bear evidence of interaction with basic melt: mafic veinlets; wide variations in mineral composition; enrichment of minerals in highly incompatible elements (Na, Zr, and LREE); enrichment of minerals in moderately incompatible elements (Ti, Y, and HREE) from P1 level to abundances 4-10 times higher toward the contacts with mafic aggregates; and exotic mineral assemblages Cr-spinel + rutile and Cr-spinel + ilmenite in peridotite and pentlandite + rutile in mafic veinlets. Anomalous incompatible-element enrichment of minerals from peridotites P2 occurred at the spinel-plagioclase facies boundary, which corresponds to pressure of about 0.8-0.9 GPa. Temperature and oxygen fugacity were estimated from spinel-orthopyroxene-olivine equilibria. Peridotites P1 with uniform mineral composition record temperature of the last complete recrystallization at 940-1050°C and FMQ buffer oxygen fugacity within the calculation error. In peridotites P2, local assemblages have different compositions of coexisting minerals, which reflects repeated partial recrystallization during heating to magmatic temperatures (above 1200°C) and subsequent reequilibration at temperatures decreasing to 910°C and oxygen fugacity significantly higher than FMQ buffer (delta log fO2 = 1.3-1.9). Mafic veins are considered to be a crystallization product from basic melt enriched in Mg and Ni via interaction with peridotite. The geochemical type of melt reconstructed by the equilibrium with Ca-pyroxene is defined as T-MORB: (La/Sm)_N~1.6 and (Ce/Yb) )_N~2.3 that is well consistent with compositional variations of modern basaltic lavas in this segment of the Mid-Atlantic Ridge, including new data on quenched basaltic glasses.

(Table 1) Geochemistry of basalts of Nauru Basin

Leg 61 of the Deep Sea Drilling Project (DSDP) was concerned with drilling a single continuously cored multiple re-entry hole at site 462 in the Central Nauru Basin (Fig. 1). Preliminary results of this drilling, which penetrated more than 1 km beneath the sea floor, were presented earlier. One major result was the discovery of a late Cretaceous off-ridge volcanic/intrusive complex of basaltic composition and great thickness (>500 m). We now present trace element abundance data for these basalts. Results of the drilling provide further support for a relatively long-lived thermal and magmatic event in the late Cretaceous resulting in voluminous and widespread magmatism in the central and western Pacific consistent with earlier suggestions. The trace element data show that most of the rocks produced during this event have trace element characteristics intermediate between those of normal and transitional mid-ocean ridge basalts (N- and T-type MORB) and different from Hawaiian basalts. These results indicate that basalts which are depleted in light rare earth elements (LREE) relative to the heavy REE may, in certain conditions, be erupted as voluminous intra-plate eruptions far from active ridge crests.

Petrology and chemistry of ODP Site 134-828 magmatic rocks

Petrography, major and trace elements, mineral chemistry, and Sr, Nd, and Pb isotopic ratios are reported for igneous rocks drilled on the northern flank of the North d'Entrecasteaux Ridge (NDR) during Ocean Drilling Program (ODP) Leg 134 Site 828. These rocks comprise a breccia unit beneath a middle Eocene foraminiferal ooze. Both geophysical characteristics and the variety of volcanic rocks found at the bottom of Holes 828A and 828B indicate that a very immature breccia or scree deposit was sampled. Basalts are moderately to highly altered, but primary textures are well preserved. Two groups with different magmatic affinities, unrelated to the stratigraphic height, have been distinguished. One group consists of aphyric to sparsely plagioclase + clinopyroxene-phyric basalts, characterized by high TiO2 (~2 wt%) and low Al2O3 (less than 15 wt%) contents, with flat MORB-normalized incompatible element patterns and LREE-depleted chondrite-normalized REE patterns. This group resembles N-MORB. The other group comprises moderately to highly olivine + plagioclase-phyric basalts with low TiO2 (<1 wt%) and high Al2O3 (usually >15 wt%) contents, and marked HFSE depletion and LFSE enrichment. Some lavas in this group are picritic, with relatively high modal olivine abundances, and MgO contents up to 15 wt%. Both the basalts and picritic basalts of this group reflect an influence by subduction-related processes, and have compositions transitional between MORB and IAT. Lavas with similar geochemical features have been reported from small back-arc basins such as the Mariana Trough, Lau Basin, Sulu Sea, and the North Fiji Basin and are referred to as back-arc basin basalts. However, regional tectonic considerations suggest that the spreading that produced these backarc basin basalts may have occurred in the forearc region of the southwest-facing island arc that existed in this region in the Eocene.

Composition of Carnian to Norian sandstones from the Wombat Plateau (Table 1)

The Carnian to Norian sediments, as much as 600 m in total thickness, recovered from ODP Sites 759 and 760 on the Wombat Plateau, are generally represented by fluvial-dominated deltaic successions. In general, the Carnian to Norian sandstones are quartzose. The average ratio of monocrystalline quartz grains, total feldspar grains, and total lithic fragments (i.e., Qm:F:Lt ratio) is 71:22:7. This indicates that they were derived mainly from the transitional continental and cratonic interior provenance terranes, such as the Pilbara Precambrian block to the south of the Wombat Plateau. The upper Carnian sediments, however, are characterized by more feldspathic sandstone petrofacies. They typically contain some volcanic rock fragments with trachytic texture and indicate the onset of the incipient rift-related tectonic movement, such as uplift and subsequent abrupt basin subsidence, together with volcanism in the Gondwana continental block. Mixed siliciclastic and carbonate cycles are typically intercalated in the prodelta to delta front deposits that developed mainly in a lagoon-like, restricted marine environment. The restricted marine environment developed during transgressions as the outflow of shallow water was restricted by depositional barriers. Around the barriers and/or delta lobes, carbonate shoals/banks were probably developed and the allochemical components of the neritic limestones may have been transported into the restricted marine environment by overwash processes and/or storm waves. Siliciclastic detritus, on the other hand, was mainly derived accompanied by delta progradation dominated by fluvial processes in the restricted marine environment. Therefore, we interpret the mixed siliciclastic and carbonate cycles in the deltaic successions to be a result of transgression-regression cycles in a deltaic system during the Late Triassic.