Geochemistry and mineralogy of garnet grains from ODP Sample 183-1137A-33R-3,50-53

On Elan Bank, a southwestern promontory of the Kerguelen Plateau in the southern Indian Ocean, we cored an interval of conglomerate and minor sandstone within a thick section of Cretaceous flood basalts. Most of the detritus in these sedimentary rocks is volcanic with the exception of a small amount of conspicuous material of probable continental derivation. The anomalous clasts include several pebbles of gneiss (Nicolaysen et al., 2001, doi:10.1130/0091-7613(2001)029<0235:POPGBG>2.0.CO;2) and garnet sand grains. The presence of continental material on the plateau bears significantly on the interpretation of Indian Ocean basalts (Weis et al., 2001, doi:10.1130/0091-7613(2001)029<0147:OOCCII>2.0.CO;2). The purpose of the present study was to determine the composition of the garnets to provide additional constraints on the nature of the source area.

Pollen profile and age determination of sediment core Schwanengrabenrinne, Brandenburg, Germany

In der Döberitzer Heide nördlich von Potsdam wurden vegetationsgeschichtliche Untersuchungen durchgeführt. Das Untersuchungsgebiet befindet sich im östlichen Teil der Nauener Platte, die bisher vegetationsgeschichtlich weitgehend unerforscht war. In sechs verschiedenen Mooren wurden acht Bohrungen niedergebracht. Die Bohrkerne wurden stratigraphisch und pollenanalytisch untersucht und für die Radiocarbondatierung beprobt. Die Pollendiagramme ermöglichen die Rekonstruktion der Vegetationsentwicklung der terrestrischen Standorte und der Moore in der Döberitzer Heide in den letzten 14.000 Jahren. Neben einer Revision der Gliederungsprinzipien der spätglazialen Vegetationsentwicklung Brandenburgs und einer vergleichenden Betrachtung der Moorentwicklung in der Döberitzer Heide wurde besonderes Augenmerk auf die Geschichte des Döberitzer Lindenwaldes gerichtet, der einen Sonderfall in der brandenburgischen Vegetation darstellt. Die Untersuchungen boten die Möglichkeit, die Ursachen seiner Entstehung zu klären, Aussagen zu den Perspektiven seiner Entwicklung zu treffen und mögliche Entwicklungspotentiale von Lindenwäldern im Land Brandenburg aufzuzeigen.

Pollen record from Muggesfelder See and Plussee in Germany

A basaltic tephra layer consisting of brownish-olive glass shards. and about 0.2 mm thick. was found in cores from four lakes in northwest Germany. According to pollen analysis it was deposited during the early Boreal period (corresponding to about 8700 BP). The petrographic properties. the geochemical composition and the age agree with those of the Saksunarvatn tephra. which was first found on the Faroe Islands. The position of the tephra layer in the pollen stratigraphy and in the absolute time-scale is discussed. Procedures for locating the tephra in other cores are suggested.

Chemical composition of sediments from DSDP Hole 149

The diagenesis and geochemical evolution of deep-sea sediments are controlled by the interaction between sediments and their associated pore waters. With increasing depth, the pore water of Hole 149 (DSDP) exhibits a strong depletion in Mg and a corresponding enrichment in Ca, while the alkalinity remains relatively constant. Dissolved SiO2 is nearly constant in the upper 100 m of sediment, but is highly enriched in the deepest pore waters. The pore waters exhibit a depletion in K with increasing depth, and O18/O16 pore water ratios also decrease. The sediment section has three zones of sedimentary regimes with increasing depth in the drill hole: an upper 100 m section of detrital clays, a middle section enriched in calc-akalic volcanics which have undergone submarine weathering to a smectite phase, and a lower section of siliceous ooze which still has a diagenetic smectite phase. The quartz-feldspar ratios and O18/O16 composition of the silicate phases are in agreement with these interpretations. The submarine weathering of volcanics to a smectite can account for the observed pore water gradients. Volcanics release Ca and Mg to the pore waters causing the alkalinity values to increase. Smectite is formed, depletes the pore waters in Mg and O18 and causes the alkalinity to decrease. The net reaction allows for the observed relationship between pore water Ca and Mg gradients with little net change in alkalinity. Given the abundance of volcanics in many deep-sea sediments, especially in lower sections which often form near ridge crests, the submarine formation of smectite may be an additional oceanic Mg sink which has not yet been fully considered.

(Table 1) Calcite, siderite, and stable isotopes d13C and d18O at DSDP Hole 93-603B

Diagenesis of the fine-grained, feldspathic sandstones in the Lower Cretaceous submarine fan complex cored in DSDP Hole 603B can be considered to have occurred in three stages: (1) replacement of matrix and framework grains by pyrite, siderite, phillipsite (?), and particularly by ferroan calcite; (2) dissolution of ferroan calcite and feldspars to produce secondary macroporosity; and (3) development of sparse feldspar and quartz overgrowths, and authigenic modification of remnant matrix. Only ferroan calcite is a volumetrically important diagenetic mineral phase (up to 50 vol.%). Matrix in thin sandstone turbidite deposits has been extensively replaced by ferroan calcite. Carbon stable isotope data suggest that organic diagenesis had only a minor influence on calcite precipitation. Oxygen stable isotope data indicate that the minimum average calcite precipitation temperature was 40° C. Preliminary calculations show that steadystate diffusion of Ca+ + from the dissolution of nannoplankton skeletal material in the interbedded pelagic marls to the associated sandstones is a feasible transport mechanism. A thick sandstone unit from 1234-1263 m sub-bottom is extensively replaced by calcite near the upper and lower contacts. Farther into the sand body away from the contacts, the sandstone has good secondary porosity resulting from the dissolution of ferroan calcite that partially replaced matrix and framework grains. The central portion of the thick sand appears to be a channel with high-energy clean sand. We believe that the channel provided a conduit for focused flow of diagenetic compactional fluids responsible for dissolution. Focused flow may be the result of the earlier lithification of the pelagic limestones and thin-bedded sandstones which, then formed vertical permeability barriers. Calcite dissolution has occurred and may still be occurring at temperatures less than 65°C.

Results of n-alkane biomarker analyses and paleoclimate reconstruction

The current study presents quantitative reconstructions of tree cover, annual precipitation and mean July temperature derived from the pollen record from Lake Billyakh (65°17'N, 126°47'E, 340 m above sea level) spanning the last ca. 50 kyr. The reconstruction of tree cover suggests presence of woody plants through the entire analyzed time interval, although trees played only a minor role in the vegetation around Lake Billyakh prior to 14 kyr BP (<5%). This result corroborates low percentages of tree pollen and low scores of the cold deciduous forest biome in the PG1755 record from Lake Billyakh. The reconstructed values of the mean temperature of the warmest month ~8-10 °C do not support larch forest or woodland around Lake Billyakh during the coldest phase of the last glacial between ~32 and ~15 kyr BP. However, modern cases from northern Siberia, ca. 750 km north of Lake Billyakh, demonstrate that individual larch plants can grow within shrub and grass tundra landscape in very low mean July temperatures of about 8 °C. This makes plausible our hypothesis that the western and southern foreland of the Verkhoyansk Mountains could provide enough moist and warm microhabitats and allow individual larch specimens to survive climatic extremes of the last glacial. Reconstructed mean values of precipitation are about 270 mm/yr during the last glacial interval. This value is almost 100 mm higher than modern averages reported for the extreme-continental north-eastern Siberia east of Lake Billyakh, where larch-dominated cold deciduous forest grows at present. This suggests that last glacial environments around Lake Billyakh were never too dry for larch to grow and that the summer warmth was the main factor, which limited tree growth during the last glacial interval. The n-alkane analysis of the Siberian plants presented in this study demonstrates rather complex alkane distribution patterns, which challenge the interpretation of the fossil records. In particular, extremely low n-alkane concentrations in the leaves of local coniferous trees and shrubs suggest that their contribution to the litter and therefore to the fossil lake sediments might be not high enough for tracing the Quaternary history of the needleleaved taxa using the n-alkane biomarker method.

Pollen record and age determinations of a profile at Cape Mamontov Klyk, Siberia

Non-glaciated Arctic lowlands in north-east Siberia were subjected to extensive landscape and environmental changes during the Late Quaternary. Coastal cliffs along the Arctic shelf seas expose terrestrial archives containing numerous palaeoenvironmental indicators (e.g., pollen, plant macro-fossils and mammal fossils) preserved in the permafrost. The presented sedimentological (grain size, magnetic susceptibility and biogeochemical parameters), cryolithological, geochronological (radiocarbon, accelerator mass spectrometry and infrared-stimulated luminescence), heavy mineral and palaeoecological records from Cape Mamontov Klyk record the environmental dynamics of an Arctic shelf lowland east of the Taymyr Peninsula, and thus, near the eastern edge of the Eurasian ice sheet, over the last 60 Ky. This region is also considered to be the westernmost part of Beringia, the non-glaciated landmass that lay between the Eurasian and the Laurentian ice caps during the Late Pleistocene. Several units and subunits of sand deposits, peat-sand alternations, ice-rich palaeocryosol sequences (Ice Complex) and peaty fillings of thermokarst depressions and valleys were presented. The recorded proxy data sets reflect cold stadial climate conditions between 60 and 50 Kya, moderate inderstadial conditions between 50 and 25 Kya and cold stadial conditions from 25 to 15 Kya. The Late Pleistocene to Holocene transition, including the Allerød warm period, the early to middle Holocene thermal optimum and the late Holocene cooling, are also recorded. Three phases of landscape dynamic (fluvial/alluvial, irregular slope run-off and thermokarst) were presented in a schematic model, and were subsequently correlated with the supraregional environmental history between the Early Weichselian and the Holocene.

Gezamlṭe shrifṭn /

1. bd. Ṭolsṭoy, Niṭshe un Ḳarl Marḳs -- 2. bd. Naṭur filozofisher maṭerializm -- 3. bd. Hisṭorishe ideen farbindungen -- 4. bd. Natsyonaliṭeṭ un progrem -- 5. bd. In ḳamf far folḳ un shprakh -- 6. bd. Der eḳonomisher maṭerializm un di natsyonale frage -- 7. bd. Di moral filozofie un der end-tsil -- 8. bd. In shṿere tsayṭen -- 9. bd. Der tsienizm un der nayer yishev in Erets Yiśroel -- 10. bd. Di Rusishe reṿolutsye un dos yidishe folḳ -- 11. bd. Iyov un Fausṭ -- 12. bd. Alberṭ Aynshṭayns ṭeorye fun relaṭiṿiṭeṭ -- 13. bd. Der sotsyalizm un di natsyonale frage -- 14. bd. Oyf di ṿegn fun modernem gedanḳengang -- 15. bd. Hoypṭ-problemen fun sotsyalizm.

Affirmative action programs.

A collection of photocopies of documents, chiefly from university libraries, assembled by the Systems and Procedures Exchange Center, and accompanied by SPEC flyer no. 67, Sept. 1980.

Investigation of the dynamics of ionized media (plasmas)

"ARL 65-91."

Helium injection into the boundary layer at an axisymmetric stagnation point

"Contract no. AF 33(616)-7661, Project no. 7064, Task no. 70169."

Apparate und Arbeitsmethoden zur mikroskopischen Untersuchung kristallisierter Körper /

Includes index.

Mtatsakan aghōtʻkʻ kitabı : jermeṛandutʻiwntan yapılmış anahtar, ki açar günahlar ile kapanmış yüreklerin kapusunu /

Mode of access: Internet.