Extremely deep-draft iceberg scouring in the glacial North Atlantic Ocean

Side-scan sonar and sub-bottom profiling investigations of the Iceland-Faeroe Ridge have revealed the widespread presence of iceberg plowmarks at water depths between 750 and 860 m. This is well beyond the maximum water depth reported for ice scouring in the adjacent areas of the North Atlantic. An exceptionally deep iceberg plowmark was found at the southern flank of the ridge, which could be traced down to 940 m water depth. Supported by published nearby sediment core data, a Saalian (MIS 6) age of that iceberg plowmark is suggested. Considering a glacial sea level of 120 m below present, the paleo-draft of this iceberg is estimated to have been at least 820 m. The keel depth of such giant icebergs drifting in the glacial northern North Atlantic significantly exceeds the draft dimensions of large icebergs seen today in the Antarctic. The most likely source area for this extreme deep-draft type of iceberg is inferred to be southern Greenland. Plowmark direction, which in our case indicates iceberg entrainment by the North Atlantic Current, is suggested to be a useful indicator of (sub)surface paleo-circulation during late Pleistocene iceberg surging and deglaciation episodes.     

Halogenation processes linked to red wood ant nests (<Emphasis Type="Italic">Formica</Emphasis> spp.) and tectonics

We investigated and evaluated the occurrence of fault zone tracer gases (CO₂, He, Rn), volatile organohalogens (CH₃Cl, CHCl₃, CHBr₃), alkanes and limonene in soil and nest gases of red wood ants (RWA) in comparison to ambient air, in a seismically active area. In this new approach, we compared RWA-free areas to RWA-areas by combining different investigation and analytical methods. In soil gas, the fault zone tracer gas Rn was surprisingly highly correlated to limonene, suggesting a combination of biotic production of limonene and abiotic degassing of Rn in a seismically active area; moderate correlations were found with trihalomethanes and other halocarbons. In RWA nests a variety of elevated concentrations of haloforms were found, while remaining below the atmospheric background values in RWA-free areas. The evidence of CHCl₃ in RWA nests is the first record. Its average concentrations in nests of F. rufa and F. polyctena were up to 3 fold higher than atmospheric background and up to 28–70 fold higher compared to e.g. volcanic emissions being considered as one of its main geogenic sources. Thus, RWA nests could possibly be an additional source for CHCl₃ liberation. Consequently, apart from RWA being bioindicators for seismically active degassing faults, they might also be used as bioindicators for CHCl₃ formation in forest soils. Although we cannot yet differentiate between a geogenic/abiotic and a biotic formation. RWA nests will have to be reconsidered for halocarbon formation in future quantifications of geochemical cycles at global scale, since they impact organic soil chemistry through biotic and/or abiotic pathways. Therefore, further larger-scale research in different tectonic settings but also in well-known CHCl₃ “hot spot” study areas such as the Klosterhede area (Denmark) should focus directly on gas sampling from confirmed active fault systems. Nests of other ant species should be addressed to compare seasonal, diurnal and nocturnal variations of degassing procedures in relation to earth tides, different geologic settings, and tectonic events such as earthquakes and on quantifying the fluxes to the atmosphere.     

Die Diatomeenflora des Beckens

Ohne Zusammenfassung     

Tagung der Internationalen Union für Geodäsie und Geophysik in Brüssel vom 20. August bis 2. September 1951

Ohne Zusammenfassung     

Die Diatomeenflora diluvialer Sedimente bei dem Dorfe Gaj bei Konin im Warthegebiet

Ohne Zusammenfassung Aus der Hydrobiologischen Anstalt der Kaiser-Wilhelm-Gesellschaft Mit 16 Abbildungen im Text     

Sonnen- und Himmelsstrahlung im Meer und in Gewässern

Zusammenfassung Die Strahlungsverhältnisse der Meere und Gewässer sind für die Ozeanographie und Seenkunde, für die Biologie, die Meteorologie und auch für die Astrophysik von Interesse. Die im vorliegenden ersten Teile bearbeitete Theorie der Reflexion von Wasserflächen ist auch für verschiedene klimatisch-energetische Probleme grundlegend. Zunächst werden die Gesetze vonSnellius undFresnel erörtert und in eine für die geophysikalische Anwendung geeignete Form gebracht, sowie tabellarisch dargestellt. Eine alte für Integrationen sehr praktische Formel vonBouguer für den Betrag der Reflexion in Abhängigkeit vom Einfallswinkel wird in Erinnerung gebracht (Formel 5 d). Die Größe des Brechungsindex in Abhängigkeit von der Temperatur, von der Wellenlänge und vom Salzgehalt des Meeres wird diskutiert. Dann wird die gesamte Reflexion einer ganz von Wasser bedeckten Erdkugel integriert, und zwar sowohl mit der Bouguerschen Näherungsformel, als auch mit der von uns transformierten Fresnelschen Formel, wobei man die Lösungen für die beiden Polarisationskomponenten der Strahlung getrennt erhält. Die durchschnittliche Reflexion einer ganz mit Wasser bedeckten Kugel ist 6,6%, während in Lehrbüchern noch vielfach der alte Zahlenwert von 21,5%, der den Beobachtungen völlig widerspricht, zu finden ist.Ferner werden auf Grund unseres normierten Tagesganges der Sonnenstrahlung für die klimatologische anwendung für alle Zonen der Erde geeignete Tabellen der Reflexionsbeträge in Abhängigkeit von der mittägigen Sonnenhöhe abgeleitet. Auch für die Reflexion der Himmelsstrahlung lassen sich mit Hilfe der Bouguerschen Formel leicht Grenzwerte für diesen Reflexionsbetrag finden, welche im Prinzip zwischen 2% als Minimum und 35% als Maximum liegen. Bei sehr hellem Horizonthimmel ist ein Betrag von 17,7% wahrscheinlich, bei vollkommen diffusem Himmelslicht ergibt sich ein Betrag von 6,6%, während die Theorie vonW. Schmidt auch hiefür 21,5% angenommen hatte. Schließlich ergibt die Theorie ein Emissionsvermögen des Wassers von 0,9535.Die innere Reflexion vollkommen diffusen inneren Streulichtes des Wassers wird zu 48,3% gefunden. Während also der Eintritt voll diffuser Strahlung zu 93% gelingt, können nur 52% aus dem Wasser in Luft heraus. Eine Theorie vonA. Ångström über die Reflexion am Grunde der Gewässer wird erweitert. Eine alte Theorie vonCh. Soret über die Reflexion an wellenbewegten Wasserspiegeln wird auf den Fall der steilsten Sturmwellen der Ozeane (Michell-Wellen) angewendet. Schließlich wird eine gute Übereinstimmung zwischen den Beobachtungen über die Reflexion verschiedener Meere und Gewässer und unserer Theorie nachgewiesen.

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Summary Radiation condtions of oceans and inland waters concern oceanography and limnology as well as biology, meteorology, and astrophysics. The theory of reflection of water-surfaces treated in the first part of this investigation is fundamental also for various climatic-energetic problems. First the laws ofSnellius andFresnel are discussed, developed into a form suitable for geophysical application, and tabulated. An old formula ofBouguer giving the amount of reflection in dependence on the angle of incidence, which can be integrated easily, is recalled (formula 5d). The refraction index in relation to temperature, wave length, and proportion of salt of the ocean is discussed. Then the total reflection of a globe entirely covered by water is integrated by means of the approximation formula ofBouguer as well as by the formula ofFresnel, transformed by the author, yielding separate solutions for the two polarisation components of radiation. The average reflection of a globe entirely covered by water amounts to 6.6 per cent, the old value of 21.5 per cent which still can be found in many text-books being in absolute contradiction with the observations.Moreover, on the basis of the normalized daily variation of solar radiation of the author, tables of reflection values suitable for climatological application to all zones of the earth are derived in dependence on the midday sun's altitude. The extreme values of reflection of the sky radiation too can be easily obtained with the aid of the formula ofBouguer varying essentially between a minimum of 2 per cent and a maximum of 35 per cent. With very clear sky at the horizon an amount of 17.7 per cent is probable, with entirely diffuse sky-light 6.6 per cent result, in contradiction to the theory ofW. Schmidt who assumed 21.5 per cent also for this value. Finally the theory gives a value of 0.9535 for the emission power of water.The inner reflection of completely diffuse light within water is found to be 48.3 per cent. Since completely diffuse radiation penetrates into water with 93 per cent, only 52 per cent can be emitted from it into the air. A theory byA. Ångström on the reflection on the bottom of waters is extended. An old theory byCh. Soret on the reflection of water-surfaces agitated by waves is applied to the steepest storm-waves of the oceans (Michell-waves). At least the good agreement of the author's theory with the observations on the reflection of various oceans and inland waters is demonstrated.

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Résumé Les conditions de rayonnement des mers et des cours d'eau en général intéressent l'océanographie, la limnologie, la biologie, la météorologie ainsi que l'astrophysique. La théorie de la réflexion des surfaces d'eau présentée dans la première partie de ce travail est également fondamentale pour différents problèmes d'énergétique climatologique. On mentionne tout d'abord les lois deSnellius et deFresnel et on leur donne une forme convenant aux applications géophysiques, accompagnée de tables numériques. On rappelle une ancienne formule deBouguer très pratique pour l'intégration et qui fournit la part d'énergie réfléchie en fonction de l'angle d'incidence (formule 5d). On discute la grandeur de l'indice de réfraction en fonction de la température, de la longueur d'onde et de la salinité de l'eau de mer. Puis on intègre la réflexion globale d'un globe entièrement recouvert d'eau, cela aussi bien au moyen de la formule d'approximation deBouguer qu'à l'aide de la formule deFresnel transformée par l'auteur, ce qui conduit aux valeurs séparées des deux composantes de polarisation du rayonnement. La réflexion moyenne d'un globe entièrement recouvert d'eau est de 6.6%, alors que les traités indiquent souvent l'ancienne valeurs de 21.5% que l'expérience contredit absolument.On établit ensuite, sur la base de la «variation diurne normalisée du rayonnement solaire» de l'auteur, des tables donnant la fraction d'énergie réfléchie en fonction de la hauteur solaire à midi, tables qui peuvent trouver emploi dans la climatologie de toutes les zones terrestres. La formule deBouguer fournit aussi sans difficulté les valeurs extrêmes de la fraction réfléchie du rayonnement céleste, lesquelles varient en principe entre un minimum de 2% et un maximum de 35%. Par ciel très clair la fraction d'énergie réfléchie probable est de 17.7%; par lumière tout à fait diffuse, elle est de 6.6%, tandis queW. Schmidt avait admis 21.5%. Enfin la théorie conduit à un pouvoir émissif de l'eau de 0.9535.On a trouvé pour la réflexion interne d'une lumière entièrement diffusée dans l'eau une valeur de 48.3%. Alors qu'un rayonnement entièrement diffus pénètre dans l'eau à raison de 93%, il n'en peut sortir que 52%. On élargit une théorie deA. Ångström concernant la réflexion au fond des eaux; on applique une ancienne théorie deCh. Soret de la réflexion sur des surfaces liquides agitées au cas des vagues les plus déclives des océans (vagues deMichell). Enfin on constate un bon accord entre les observations de réflexion de différentes mers ou de cours d'eau et la théorie de l'auteur.

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Mit 8 Textabbildungen.

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Herrn Prof.Dr. Franz Ruttner, dem Leiter der Biologischen Station Lunz am See und Fachmann der Strahlungsverhältnisse im Wasser, zur Feier seines 70. Geburtstages am 12. Mai 1952 gewidmet.     

Hf-W mineral isochron for Ca,Al-rich inclusions: Age of the solar system and the timing of core formation in planetesimals

Application of ¹⁸²Hf-¹⁸²W chronometry to constrain the duration of early solar system processes requires the precise knowledge of the initial Hf and W isotope compositions of the solar system. To determine these values, we investigated the Hf-W isotopic systematics of bulk samples and mineral separates from several Ca,Al-rich inclusions (CAIs) from the CV3 chondrites Allende and NWA 2364. Most of the investigated CAIs have relative proportions of ¹⁸³W, ¹⁸⁴W, and ¹⁸⁶W that are indistinguishable from those of bulk chondrites and the terrestrial standard. In contrast, one of the investigated Allende CAIs has a lower ¹⁸⁴W/¹⁸³W ratio, most likely reflecting an overabundance of r-process relative to s-process isotopes of W. All other bulk CAIs have similar ¹⁸⁰Hf/¹⁸⁴W and ¹⁸²W/¹⁸⁴W ratios that are elevated relative to average carbonaceous chondrites, probably reflecting Hf-W fractionation in the solar nebula within the first ∼3 Myr. The limited spread in ¹⁸⁰Hf/¹⁸⁴W ratios among the bulk CAIs precludes determination of a CAI whole-rock isochron but the fassaites have high ¹⁸⁰Hf/¹⁸⁴W and radiogenic ¹⁸²W/¹⁸⁴W ratios up to ∼14 ε units higher than the bulk rock. This makes it possible to obtain precise internal Hf-W isochrons for CAIs. There is evidence of disturbed Hf-W systematics in one of the CAIs but all other investigated CAIs show no detectable effects of parent body processes such as alteration and thermal metamorphism. Except for two fractions from one Allende CAI, all fractions from the investigated CAIs plot on a single well-defined isochron, which defines the initial ε¹⁸²W = −3.28 ± 0.12 and ¹⁸²Hf/¹⁸⁰Hf = (9.72 ± 0.44) × 10⁻⁵ at the time of CAI formation. The initial ¹⁸²Hf/¹⁸⁰Hf and ²⁶Al/²⁷Al ratios of the angrites D’Orbigny and Sahara 99555 are consistent with the decay from initial abundances of ¹⁸²Hf and ²⁶Al as measured in CAIs, suggesting that these two nuclides were homogeneously distributed throughout the solar system. However, the uncertainties on the initial ¹⁸²Hf/¹⁸⁰Hf and ²⁶Al/²⁷Al ratios are too large to exclude that some ²⁶Al in CAIs was produced locally by particle irradiation close to an early active Sun. The initial ¹⁸²Hf/¹⁸⁰Hf of CAIs corresponds to an absolute age of 4568.3 ± 0.7 Ma, which may be defined as the age of the solar system. This age is 0.5-2 Myr older than the most precise ²⁰⁷Pb-²⁰⁶Pb age of Efremovka CAI 60, which does not seem to date CAI formation. Tungsten model ages for magmatic iron meteorites, calculated relative to the newly and more precisely defined initial ε¹⁸²W of CAIs, indicate that core formation in their parent bodies occurred in less than ∼1 Myr after CAI formation. This confirms earlier conclusions that the accretion of the parent bodies of magmatic iron meteorites predated chondrule formation and that their differentiation was triggered by heating from decay of abundant ²⁶Al. A more precise dating of core formation in iron meteorite parent bodies requires precise quantification of cosmic-ray effects on W isotopes but this has not been established yet.     

High resolution magnetostratigraphy and deposition cycles in the Nihewan Basin (North China) and their significance for stone artifact dating

Three lacustrine sections in the Nihewan Basin, Xiaodukou, Donggutuo and Xiaochangliang (40.1-40.4°N; 114.6-114.7°E), were closely sampled for magnetostratigraphic and deposition cycle analysis. Rock magnetic investigations show that the characteristic remanent magnetization of the sediments is mainly carried by magnetite and hematite. The Xiaodukou sequence is one of the most complete sections in the basin and has recorded substantial parts of the Brunhes and Matuyama chrons back to the termination of the Olduvai subchron. Several subchrons within the Matuyama period have been documented such as the Jaramillo, the Cobb Mt. and others. The Matuyama/Brunhes boundary, the Jaramillo, as well as the Cobb Mountain events were observed also at Donggutuo. On the basis of grain size and susceptibility data and of field investigations, the sections are divided into two longer lasting lacustrine episodes with a fluvio-lacustrine deposit in between. They are structured by 15 high-frequency deposition sub-cycles. In each cycle, the grain size fines upwards, while magnetic susceptibility decreases. This behavior is due to cyclic water level change of the ancient lake Nihewan. At Xiaodukou, the variations of the 0.2 to 7.5 μm grain size fraction can be correlated with the marine oxygen isotope stages OIS 64-OIS 11. The grey-green clayey to silty Paleolithic stone artifact layers at Xiaochangliang and Donggutuo are located at depths of 55.4 m and 43-38.7 m, respectively. They were buried when the lake-level was rising. The artifact layers have been deposited around the Cobb Mountain event during the sedimentary sub-cycle 6 of the older lacustrine phase corresponding to OIS 35, 36. Thus in contrast to the results of other studies, the estimated age of the Xiaochangliang stone artifact layer does not exceed 1.26 Ma, while the Donggutuo stone artifact layers date back to 1.21-1.15 Ma. This age determination brings the Nihewan hominids in close relation to the findings of Homo Erectus at Lantian on the Chinese Loess Plateau.     

SWAT.nz: New-Zeland-based “Sand Waves and Turbulence” experimental programme

The SWAT.nz (“New-Zealand-based Sand Waves and Turbulence”) research programme was carried out to advance understanding of subaqueous sand waves. The programme was based around detailed measurements at varying scales of bed morphologies and associated flow fields as sand waves formed from plane-bed conditions and grew to equilibrium. This paper outlines the philosophy and details of the SWAT.nz programme, with the aim of providing insight into experiment and analysis design and methodologies for studies of highly-variable bed surfaces and flows. Example challenges addressed in the SWAT.nz programme include the measurement over large spatial domains of developing flow fields and three-dimensional bed morphology, including flow measurements below roughness (sand-wave) crests, and how to interpret the collected measurements. Insights into sand-wave dynamics that have arisen from the programme are presented to illustrate the values of the SWAT.nz programme and the developed methodologies. Results are presented in terms of mobile-bed processes, and flow-bed interaction and flow processes for fixed-bed roughness and erodible beds, respectively.