Grain size analysis of sediment coring site CRP-2 from the Ross Sea, Antarctica

The purpose of this note is to present results of grain size analyses from 118 samples of the CRP-2/2A core using sieve and Sedigraph techniques. The samples were selected to represent the range of facies encountered, and tend to become more widely spaced with depth. Fifteen came from the upper 27 m of Quaternary and Pliocene sediments, 62 from the early Miocene-late Oligocene strata (27 to 307 mbsf), and 41 from the early Oligocene strata beneath (307 to 624 mbsf). The results are intended to provide reference data for lithological descriptions in the core logs (Cape Roberts Science Team, 1999), and to help with facies interpretation. The analytical technique used for determining size frequency of the sand fraction in our samples (sieving) is simple, physical and widely practised for over a century. Thus it provides a useful reference point for analyses produced by other faster and more sophisticated techniques, such as the Malvern laser particle size analysis system (Woolfe et al., 2000), and estimates derived from measurements taken with down-hole logging tools (Bücker, pers. com., 1999).

Investigation of Quaternary foraminifera in sediment core CRP-1 from the Ross Sea, Antarctica

Foraminifera are examined in twenty-six samples from a 44 metre succession of Quaternary glacial sediments recovered from the CRP-1 drillhole on Roberts Ridge, southwestern Ross Sea, Antarctica. In situ marine assemblages were documented in at least three of the six lithostratigraphic units, and it is likely that the remaining three interbedded diamicton units are also marine in origin. Peak foraminiferal diversities are documented in Unit 3.1 (73 species) and Unit 2.2 (32 species). Calcareous benthics dominate the assemblages, but may be accompanied by abundant occurrences of the planktonic Neogloboquadrina pachyderma. Low diversity agglutinated faunas appear in the uppermost strata of Units 4.1 and 2.2. A close relationship between lithofacics and foraminiferal biofacies points to marine environments that alternated between proximity to and distance from active glaciers and iceshelf fronts, with associated variations in salinity, sea-surface ice cover and the levels of rainout from debris-laden ice.

Analysis of Recent benthic foraminiferal assemblages from the oxygen minimum zone of the Pakistan continental margin

Live (Rose Bengal stained) and dead benthic foraminiferal communities (hard-shelled species only) from the Pakistan continental margin oxygen minimum zone (OMZ) have been studied in order to determine the relation between faunal composition and the oxygenation of bottom waters. During R.R.S. Charles Darwin Cruises 145 and 146 (12 March to May 28 2003), 11 multicores were taken on the continental margin off Karachi, Pakistan. Two transects were sampled, constituting a composite bathymetric profile from 136 m (above the OMZ in spring 2003) down to 1870 m water depth. Cores (surface area 25.5 cm2) were processed as follows: for stations situated above, and in the upper part of the OMZ, sediment slices were taken for the 0-0.5 and 0.5-1 cm intervals, and then in 1 cm intervals down to 10 cm. For the lower part of the OMZ, the second centimetre was also sliced in half-centimetre intervals. Each sample was stored in 10 % borax-buffered formalin for further processing. Onshore, the samples were wet sieved over 63 µm, 150 µm and 300 µm sieves and the residues were stained for one week in ethanol with Rose Bengal. After staining, the residue was washed again. The stained faunas were picked wet in three granulometric fractions (63-150 µm, 150-300 µm and >300 µm), down to 10 cm depth. To gain more insight into the population dynamics we investigated the dead (unstained) foraminifera in the 2-3 cm level for the fractions 150-300 µm and >300 µm. The fractions >300 µm and 150-300 µm show nearly the same faunal distribution and therefore the results are presented here for both fractions combined (i.e. the >150 µm fraction). Live foraminiferal densities show a clear maximum in the first half centimetre of the sediment; only few specimens are found down to 4 cm depth. The faunas exhibit a clear zonation across the Pakistan margin OMZ. Down to 500 m water depth, Uvigerina ex gr. U. semiornata and Bolivina aff. B. dilatata dominate the assemblages. These taxa are largely restricted to the upper cm of the sediment. They are adapted to the very low bottom-water oxygen values (ab. 0.1 ml/l in the OMZ core) and the extremely high input of organic carbon on the upper continental slope. The lower part of the OMZ is characterized by cosmopolitan faunas, containing also some taxa that in other areas have been described in deep infaunal microhabitats.

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

Early Oligocene siliceous microfossils were recovered in the upper c. 193 m of the CRP-3 drillcore. Although abundance and preservation are highly variable through this section, approximately 130 siliceous microfossil taxa were identified, including diatoms, silicoflagellates, ebridians, chrysophycean cysts, and endoskeletal dinoflagellates. Well-preserved and abundant assemblages characterize samples in the upper c. 70 m and indicate deposition in a coastal setting with water depths between 50 and 200 m. Abundance fluctuations over narrow intervals in the upper c. 70 mbsf are interpreted to reflect environmental changes that were either conducive or deleterious to growth and preservation of siliceous microfossils. Only poorly-preserved (dissolved, replaced, and/or fragmented) siliceous microfossils are present from c. 70 to 193 mbsf. Diatom biostratigraphy indicates that the CRP-3 section down to c. 193 mbsf is early Oligocene in age. The lack of significant changes in composition of the siliceous microfossil assemblage suggests that no major hiatuses are present in this interval. The first occurrence (FO) of Cavitatus jouseanus at 48.44 mbsf marks the base of the Cavitatus jouseanus Zone. This datum is inferred to be near the base of Subchron C12n at c. 30.9 Ma. The FO of Rhizosolenia antarctica at 68.60 mbsf marks the base of the Rhizosolenia antarctica Zone. The FO of this taxon is correlated in deep-sea sections to Chron C13 (33.1 to 33.6 Ma). However, the lower range of R. antarctica is interpreted as incomplete in the CRP-3 drillcore, as it is truncated at an underlying interval of poor preservation: therefore, an age of c. 33.1 to 30.9 Ma is inferred for interval between c. 70 and 50 mbsf. The absence of Hemiaulus caracteristicus from diatom-bearing interval of CRP-3 further indicates an age younger than c. 33 Ma (Subchron C13n) for strata above c. 193 mbsf. Siliceous microfossil assemblages in CRP-3 are significantly different from the late Eocene assemblages reported CIROS-1 drillcore. The absence of H. caracteristicus, Stephanopyxis splendidus, and Pterotheca danica, and the ebridians Ebriopsis crenulata, Parebriopsis fallax, and Pseudoammodochium dictyoides in CRP-3 indicates that the upper 200 m of the CRP-3 drillcore is equivalent to part of the stratigraphic interval missing within the unconformity at c. 366 mbsf in CIROS-1.

Las bibliotecas populares en la Argentina entre 1870 y 1875 : La construcción de una política bibliotecaria

El artículo trata sobre la institución de las bibliotecas populares en la Argentina entre 1870 y 1875. Mediante el estudio de diversos documentos, se analizan los siguientes aspectos y sus mutuas relaciones: a. las vinculaciones entre la sociedad civil y el Estado implícitas en el dispositivo legal de fomento a las bibliotecas; b. las responsabilidades asumidas por oficina gubernamental a cargo la política bibliotecaria y la manera en que se construyó un saber especializado en la materia; c. el papel preponderante del Boletín de las bibliotecas populares como instancia de articulación entre las asociaciones y el Estado; d. los resultados cuantitativos obtenidos en la fase fundacional. En el cierre del trabajo se valoran los resultados expuestos en función de la significación histórica que tiene este período como inauguración de una manera concebir la expansión de las bibliotecas de acceso público

Hacer las reglas del hacer : Concepciones y rutinas bibliotecarias en los reglamentos de las bibliotecas populares en la Argentina (1870-1875)

El artículo aborda los vínculos sostenidos por la Comisión Protectora de las Bibliotecas Populares y las bibliotecas populares con relación a la elaboración de reglas adecuadas para ordenar el funcionamiento de estas instituciones. A partir de un análisis del Boletín de las Bibliotecas Populares, se estudia la manera en que la Comisión insistió en la difusión de dos servicios: la lectura gratuita en la sala y el préstamo domiciliario de libros a cambio de una cuota accesible. Se observa cómo las bibliotecas incorporaron progresivamente esas pautas y, al hacerlo, colaboraron con sus propios reglamentos con la estrategia pedagógica del Boletín. Se examinan, asimismo, las indicaciones técnicas presentes en la revista para contribuir con el desarrollo de los procesos bibliotecarios necesarios para sustentar dichos servicios. Se concluye que entre 1870 y 1875 estas acciones renovaron la tradición bibliotecaria en la Argentina, aun cuando es posible detectar diversas deficiencias y contrasentidos en la transmisión de esta nueva concepción bibliotecológica. Finalmente, se evalúa la pertinencia de los reglamentos y otros documentos institucionales para desenvolver los estudios históricos sobre los contextos de la lectura

Las bibliotecas populares en la Argentina entre 1870 y 1875 : La construcción de una política bibliotecaria

El artículo trata sobre la institución de las bibliotecas populares en la Argentina entre 1870 y 1875. Mediante el estudio de diversos documentos, se analizan los siguientes aspectos y sus mutuas relaciones: a. las vinculaciones entre la sociedad civil y el Estado implícitas en el dispositivo legal de fomento a las bibliotecas; b. las responsabilidades asumidas por oficina gubernamental a cargo la política bibliotecaria y la manera en que se construyó un saber especializado en la materia; c. el papel preponderante del Boletín de las bibliotecas populares como instancia de articulación entre las asociaciones y el Estado; d. los resultados cuantitativos obtenidos en la fase fundacional. En el cierre del trabajo se valoran los resultados expuestos en función de la significación histórica que tiene este período como inauguración de una manera concebir la expansión de las bibliotecas de acceso público