Accumulation rates of bulk sediment and total organic carbon for Ontong Java Plateau sediments

Organic geochemical investigations were performed on sediments of Leg 130 to reconstruct the depositional environment of the Ontong Java Plateau. The Miocene to Quaternary sediments collected during the drilling campaign are characterized by extremely low organic carbon contents. As indicated by C/N ratios and Rock-Eval data, most of the organic matter is probably of marine origin. Based on mass-accumulation rates of organic carbon, the paleoproductivity for the Miocene-Pliocene and the late Pliocene-Pleistocene time intervals as well as the modern surface-water production were estimated. The productivity values of the surface sediments (25-59 gC/m2/yr) reflect the various influences of the equatorial upwelling cell on the different sites. The accumulation rates of organic carbon are generally low; however, they show a distinct increase at 8 Ma and a decrease at 2 Ma.

Identidades hispanas en EE.UU.

Este artículo analiza el tema de la identidad hispana / latina en EE.UU. como resultado de fuerzas históricas y políticas en juego desde el siglo XVI, despejando el tema de conceptos y prejuicios raciales o étnicos que tienden a justificar actitudes discriminatorias basadas en conceptos esencialistas. La categoría de “hispanos" que nace de varios encuentros ha significado el agrupamiento en EE.UU. de pueblos en su mayoría no-sajones, y dicha agrupación lleva a preguntarse ¿qué es ser “hispano" o “latino"? El artículo propone que la identidad hispana en EE.UU. surge como una manera de responder de manera coherente a una historia política que construye identidades en base a términos raciales. En suma, la raza y las identidades que ella sostiene nacen de procesos históricos y políticos y no constituyen una categoría “natural" dada. Como resultado de estos procesos, los grupos que se formen alrededor de la raza, y no de nacionalidades o culturas, en el esquema político norteamericano, tienen más posibilidades de que su voz se escuche a nivel nacional.

Gómez Martínez, José Luis (ed.). Anuario bibliográfico de historia del pensamiento ibero e iberoamericano 1986. EE.UU., The University of Georgia, 1989, 136 p.

Fil: Jalif de Bertranou, Clara Alicia.

Necesidades de salud sexual reproductiva entre mujeres inmigrantes en San Juan (Puerto Rico), Madrid (España) y Nueva York (EE.UU): Anticoncepción y Embarazo No Deseado.

Este informe forma parte del proyecto “Necesidades, Experiencias y conocimientos en salud sexual reproductiva entre los profesionales de salud y las mujeres inmigrantes en San Juan (Puerto Rico), Madrid (España) y Nueva York (EE.UU.): Anticoncepción y Embarazo No Deseado” auspiciado por Saludpromujer, Departamento de Obstetricia y Ginecología de la Escuela de Medicina, Universidad de Puerto Rico. En esta parte de la investigación hemos explorado el acceso a los servicios de salud sexual y reproductiva (SSR) de las mujeres inmigrantes en Madrid a partir de las experiencias y conocimientos de un grupo de profesionales de la salud acerca del uso del misoprostol como alternativa para interrumpir embarazos no deseados en población inmigrante y española. Este acercamiento nos ha permitido profundizar en las necesidades en salud sexual y reproductiva del colectivo de mujeres inmigrantes en Madrid y las estrategias para satisfacerlas.

Quaternary oxygen isotope record of planktonic foraminifera from ODP Site 805 on the Ontong Java Plateau

The oxygen isotope records of G. sacculifer and Pulleniatina in the uppermost three cores at Ocean Drilling Program Hole 805C span the last 1.6 m.y., an estimate based on Fourier stratigraphy. The last 700,000 yr are dominated by both eccentricity and obliquity-related orbital fluctuations. The range of variation of delta18O values is about 1.5?, of which ca. 75% may be assigned to global ice-volume effect. The remainder of the range is shared by the effects of surface temperature variation, thermocline depth change (in the case of Pulleniatina, especially), and differential dissolution. Before 1 Ma, obliquity-related fluctuations dominate. The transition between obliquity- and eccentricity-dominated time occurs between ca. 1 and 0.7 Ma. It is marked by irregularities in phase relationships, the source of which is not clear. The age of the Brunhes/Matuyama boundary is determined as 794,000 yr by obliquity counting. However, an age of 830,000 yr also is compatible with the counts of both eccentricity and obliquity cycles. In the first case, Stage 19 (which contains the boundary) is coincident with the crest of the 19th obliquity cycle, setting the first crest downcore equal to zero, and counting backward (o19). In the second, Stage 19 coincides with o20. No evidence was found for fluctuations related to precession (23 and 19 k.y.) rising above the noise level, using plain Fourier expansion on the age model of the entire series. Detailed stratigraphic comparison with the Quaternary record of Hole 806B allows the recognition of major dissolution events (which increase the difference in delta18O values of G. sacculifer at the two sites). These occur at Stages 11-13, 16-17, and near 1.5 Ma (below o33).

Stable carbon isotope in bottom water and Cibicidoides wuellerstorfi on the Ontong Java Plateau and Emperor Seamount

We have measured the carbon isotopic composition of dissolved inorganic carbon in bottom waters of the Ontong Java Plateau (western equatorial Pacific) and on the northern Emperor Seamounts (northwest Pacific). Each of these locations is several hundred miles from the nearest Geochemical Ocean Sections Study (GEOSECS) stations, and the observed delta13C values at each site differ substantially from regionally averaged GEOSECS delta13C profiles. We discuss the possible causes of these differences, including horizontal variability, near-bottom effects, and problems with the Pacific GEOSECS delta13C data. We also measured the isotopic composition (C and O) of core top C. wuellerstorfi from a depth transect of cores at each location. The delta18O data are used to verify that our samples are Holocene. Comparison of foraminiferal and bottom water delta13C values shows that this species faithfully records bottom water delta13C at both sites and demonstrates that there is no depth-related artifact in the dissolved inorganic carbon-C. wuellerstorfi delta13C relationship at these sites.

The Fohsella chronocline in middle Miocene sediments from the Ontong Java Plateau, Pacific Ocean

Micropaleontologists have traditionally recognized the mid-Miocene Fohsella lineage as a flagship for phyletic gradualism within the planktic foraminifera. However, study of a deep-sea record from the western equatorial Pacific (ODP Site 806) reveals that coiling ratios within this clade suddenly (<5 kyr) shift after a prolonged, ancestral state of near randomness (~50%) to a transient phase (13.42-13.43 Ma) of dextral dominance (~75%) immediately following the first common occurrence of keeled fohsellids. This brief period of dextral dominance was abruptly (<5 kyr) succeeded by an irreversible change to sinistral dominance (~96%). Fohsellid abundances decline markedly through the interval in which the sinistral preference is established. The shift to sinistrality (13.42 Ma) predated the deepening of fohsellid depth ecology by ~240-488 kyr, indicating that these two events were unrelated. This view is supported by a lack of delta 18O evidence for depth-habitat differences between the two chiral forms, which refutes the notion that sinistral fohsellids were "pre-adapted" for ensuing hydrographic change because they occupied a deeper depth habitat than their dextral counterparts. Planktic foraminiferal assemblages become strongly oligotrophic in character through the interval in which the fohsellid delta 18O increase is recorded, indicating that the migration to deeper depths was fostered by an expansion of the mixed layer in the western equatorial Pacific. Salient aspects of this brief, but conspicuous faunal change are a marked increase in the abundance of symbiont-bearing globigerinoidids, a concomitant collapse of local Jenkinsella mayeri/siakensis populations, and reduced fohsellid abundances. The rapid and permanent nature of the Fohsella sinistral shift provides a distinct, unequivocal datum that may prove useful for correlating mid-Miocene sections throughout the Caribbean Sea and tropical regions in the western sectors of the Pacific and Atlantic. The coiling ratio changes that occurred during the evolution of the Fohsella chronocline probably reflect changing population dynamics between cryptic genotypes with different coiling preferences.