Iron (Fe) concentrations and fluxes in TALDICE ice core 0.6 to 314 ky BP

Atmospheric fluxes of iron (Fe) over the past 200 kyr are reported for the coastal Antarctic Talos Dome ice core, based on acid leachable Fe concentrations. Fluxes of Fe to Talos Dome were consistently greater than those at Dome C, with the greatest difference observed during interglacial climates. We observe different Fe flux trends at Dome C and Talos Dome during the deglaciation and early Holocene, attributed to a combination of deglacial activation of dust sources local to Talos Dome and the reorganisation of atmospheric transport pathways with the retreat of the Ross Sea ice shelf. This supports similar findings based on dust particle sizes and fluxes and Rare Earth Element fluxes. We show that Ca and Fe should not be used as quantitative proxies for mineral dust, as they all demonstrate different deglacial trends at Talos Dome and Dome C. Considering that a 20 ppmv decrease in atmospheric CO2 at the coldest part of the last glacial maximum occurs contemporaneously with the period of greatest Fe and dust flux to Antarctica, we confirm that the maximum contribution of aeolian dust deposition to Southern Ocean sequestration of atmospheric CO2 is approximately 20 ppmv.

La Plata en las vísperas montoneras : Una reconstrucción de las condiciones sociales y políticas de la masificación y radicalización política de la JP platense y su articulación con Montoneros (1970-72)

El trabajo trata sobre el proceso de radicalización política y masificación de Juventud Peronista de La Plata y su articulación con Montoneros. Abarcando el intenso período que puede extenderse desde mediados de 1970 hasta la vuelta de Perón a fines de 1972. Durante el mismo, la agrupación platense creció desarrollando una importante actividad política, sobre todo estudiantil y barrial, para formar parte hacia fines del '72 de la estrategia de masas de la organización Montoneros. En base a material periodístico y testimonial se busca reconstruir el 'escenario platense de la radicalización'. Es decir, por un lado las características demográficas, sociales, políticas, ideológicas locales que coadyuvaron a las movilizaciones. Por otra parte, se aborda la dinámica política. En primer término, la partidaria impulsada por la apertura electoral. Y luego, la revolucionaria acelerada por las organizaciones armadas. En ambas la JP platense se consolidó y terminó el proceso articulada con Montoneros para desarrollar posteriormente un importante 'trabajo de masas'

La Plata en las vísperas montoneras : Una reconstrucción de las condiciones sociales y políticas de la masificación y radicalización política de la JP platense y su articulación con Montoneros (1970-72)

El trabajo trata sobre el proceso de radicalización política y masificación de Juventud Peronista de La Plata y su articulación con Montoneros. Abarcando el intenso período que puede extenderse desde mediados de 1970 hasta la vuelta de Perón a fines de 1972. Durante el mismo, la agrupación platense creció desarrollando una importante actividad política, sobre todo estudiantil y barrial, para formar parte hacia fines del '72 de la estrategia de masas de la organización Montoneros. En base a material periodístico y testimonial se busca reconstruir el 'escenario platense de la radicalización'. Es decir, por un lado las características demográficas, sociales, políticas, ideológicas locales que coadyuvaron a las movilizaciones. Por otra parte, se aborda la dinámica política. En primer término, la partidaria impulsada por la apertura electoral. Y luego, la revolucionaria acelerada por las organizaciones armadas. En ambas la JP platense se consolidó y terminó el proceso articulada con Montoneros para desarrollar posteriormente un importante 'trabajo de masas'

La Plata en las vísperas montoneras : Una reconstrucción de las condiciones sociales y políticas de la masificación y radicalización política de la JP platense y su articulación con Montoneros (1970-72)

El trabajo trata sobre el proceso de radicalización política y masificación de Juventud Peronista de La Plata y su articulación con Montoneros. Abarcando el intenso período que puede extenderse desde mediados de 1970 hasta la vuelta de Perón a fines de 1972. Durante el mismo, la agrupación platense creció desarrollando una importante actividad política, sobre todo estudiantil y barrial, para formar parte hacia fines del '72 de la estrategia de masas de la organización Montoneros. En base a material periodístico y testimonial se busca reconstruir el 'escenario platense de la radicalización'. Es decir, por un lado las características demográficas, sociales, políticas, ideológicas locales que coadyuvaron a las movilizaciones. Por otra parte, se aborda la dinámica política. En primer término, la partidaria impulsada por la apertura electoral. Y luego, la revolucionaria acelerada por las organizaciones armadas. En ambas la JP platense se consolidó y terminó el proceso articulada con Montoneros para desarrollar posteriormente un importante 'trabajo de masas'

Geochemistry, SiO2 minerals and isotopes at DSDP Hole 72-516F

Cherts recovered during DSDP Leg 72 from Rio Grande Rise sediments (Site 516) consist of both cristobalite and quartz, and contain ghosts of foraminifers and (more rare) radiolarians. Porcelanite made of disordered cristobalite is found in most old enclosing sediments. Local dissolution of siliceous microfossils during diagenesis is the most likely source of the silica required for the chert formation. As sediment age increases, the proportion of biogenic silica decreases and authigenic silica increases.

Datum events and their estimated magnetochronology at DSDP Site 72-516

Calcareous plankton biostratigraphy (foraminifers and nannoplankton) and magnetostratigraphy of the upper Oligocene to Pleistocene have been studied in hydraulic piston Cores 516-1 to 516-44, 516A-5 to 516A-11, and 516F-1 to 516F-11, Rio Grande Rise (water depth 1313 m). Some 80 biostratigraphic datum events have been correlated to the magnetic polarity stratigraphy over an interval representing the Matuyama to Chron 5, and Chrons 16 to 23. Coring disturbance and biostratigraphic evidence of a condensed section preclude unambiguous identification of polarity or biostratigraphic events over an approximately 30-m interval in the middle and upper Miocene. Sedimentation rates varied considerably during the Neogene, but an abnormally thick upper Oligocene and lower Miocene section allows a high degree of magnetobiochronologic resolution. A new planktonic foraminiferal zonation for the Miocene completes the midlatitude Neogene zonation of the South Atlantic. Important magnetobiostratigraphic correlations at Site 516 and their estimated magnetochronology include: (1) Oligocene/ Miocene boundary = first appearance datum (FAD) Globorotalia kugleri = last appearance datum (LAD) Reticulofenestra bisecta = mid-Anomaly 6C (Chron 23) = 23.7 Ma; (2) Aquitanian/Burdigalian boundary = LAD G. kugleri = between base Anomaly 6A and top of unnumbered anomaly between 6A and 6B (Chron 21) = 21.8 Ma; (3) Zone N6/N7 boundary = LAD Catapsydrax dissimilis (= FAD G. pseudomiozea and G. zealandica) = Chron 16/17 boundary = 17.6 Ma; (4) early/middle Miocene (= Burdigalian/Langhian) boundary = FAD Praeorbulina sicana = midpart of Anomaly 5C (Chron 16) = 16.6 Ma or FAD P. glomerosa = just above Anomaly 5C (inferred) = 16.3 Ma; (5) Zone N8/N9 boundary = FAD Orbulina suturalis above Anomaly 5C (later part Chron 16, inferred); (6) Miocene/ Pliocene boundary = LAD Globoquadrina dehiscens LAD Globorotalia lenguaensis = basal Gilbert Chron = 5.3 Ma.

Fig. 6: Firn temperatures at Filchner Station

During the German Antarctic Expedition 1979/80 to the Filchner/Ronne Ice Shelf glaciclogical investigations were carried out at the Filchner station, mainly for determination of snow accumulation. Also meteorological measurements and observations were part of the programme. Similar glaciological work on a smaller seale was done at Atka Ice Port. The report presents the results of the glaciological investigations, In an introductory part some basie eonsiderations, definitions and methods are discussed briefly, completed by a few hints on practical snow pit work. Density measurements, stratigraphie analyses with aid of a throughlight profile and hardness determination are described in more detail. The analyses of the Fi1chner snow profile of January 1980 with suplements of January 1981 reveal 7 complete budget years for 370 cm depth or 53 cm snow accumulation/year, With a mean density of 0.377 g/cm**2 this value corresponds to a water equivalent of 20 g/cm**2. At the Atka site 3 budget years were determined within 210 cm depth of the snow pit or 70 cm of mean annual accumulaticn. With the rat her higher mean density of 0.438 g/cm**2 for this site the corresponding water equivalent amounts here to 30 g/cm**2, In addition to the snow pit studies shallow drillings were made at Filchner Station to a depth of 10.8 m with 128 sampies taken from the core and at Atka to 12.1 m depth with 114 sampies. At the Institute for Radiohydrometry, Neuherberg, the sarnples were analysed with respect to the stable isotope ratios 2H/1H and 18O/16O related to V-SMOW. Also the tritium content was measured. The vartiations of the stable isotope ratios with the depth show quasiperiodic fluctuations which are regarded as annual cycles of the accumulation rate. Counting of the pronounced peaks leads to 20 years for the Filchner core, giving 55 cm annual accumulation or 22 g/cm**2 water equivalent respectively. At Atka 15 years could be found corresponding to 75 cm annual accumulation or 32 g/cm**2 of water. The range of varianon and the mean value of the stable isotope ratios are significantly different for both sites, the agreement of the isotopic anal yses with the pit studies is rat her satisfactory. The tritium content shows for the Filchner core two pronounced peaks which can be related to the 1965 and 1966 winter seasons according to former studies at the South Pole station. These time estimates are consistent with the time scale derived fr orn the stable isotopes distribution. At the Atka site no similar effeet in the tritium values was found. In the drill holes firn temperatures were measured carefully. The 10 m value was determined to be -25 °C at Filchner Station and -17 °C at the Atka position.

Alkali contents, Sr isotope and U-Th-Pb data for ocean crust vein minerals from DSDP Holes 27-261, 61-462A, and 72-516F

Cation exchange experiments (ammonium acetate and cation resin) on celadonite-smectite vein minerals from three DSDP holes demonstrate selective removal of common Sr relative to Rb and radiogenic Sr. This technique increases the Rb/Sr ratio by factors of 2.3 to 22 without significantly altering the age of the minerals, allowing easier and more precise dating of such vein minerals. The ages determined by this technique (Site 261 - 121.4+/-1.6 m.y.; Site 462A - 105.1+/-2.8 m.y.; Site 516F - 69.9+/-2.4 m.y.) are 34, 54 and 18 m.y. younger, respectively, than the age of crust formation at the site; in the case of site 462A, the young age is clearly related to off-ridge emplacement of a massive sill/flow complex. At the other sites, either the hydrothermal circulation systems persisted longer than for normal crust (10-15 m.y.), or were reactivated by off-ridge igneous activity. Celadonites show U and Pb contents and Pb isotopic compositions little changed from their basalt precursors, while Th contents are significantly lower. Celadonites thus have unusually high alkali/U,Th ratios and low Th/U ratios. If this celadonite alteration signature is significantly imprinted on oceanic crust as a whole, it will lead to very distinctive Pb isotope signatures for any hot spot magmas which contain a component of aged subducted recycled oceanic crust. Initial Sr isotope ratios of ocean crust vein minerals (smectite, celadonite, zeolite, calcite) are intermediate between primary basalt values and contemporary sea water values and indicate formation under seawaterdominated systems with effective water/rock ratios of 20-200.