Mars: Evidence for dynamic processes from mariners 6 and 7

Mariners 6 and 7 photographs of the equatorial region of Mars document a three-stage evolution of that part of the Martian surface: (1) High- and intermediate-albedo cratered terrains in Meridiani Sinus, Margaritifer Sinus-Thymiamata, Deucalionis Regio-Sabaeus Sinus, and Hellespontus; (2) low-albedo moderately cratered terrain and dark crater fill in Meridiani Sinus, Thymiamata, and Deucalionis Regio-Sabaeus Sinus and possible volcanism in the Hellas-Hellespontus border; and (3) high-albedo surficial deposits, banked-up crater fill, a possible bright-ray crater in Meridiani Sinus, chaotic terrain on the edge of the Margaritifer Sinus mesa, featureless terrain in Hellas and Edom, sinuous channel-like reentrants on scarps at the Hellas-Hellespontus boundary. Regional faulting seems to have occurred following formation of the old cratered plains and prior to formation of low-albedo plains in Meridiani Sinus and also prior to formation of canyon-like reentrants and featureless terrain along the Hellas-Hellespontus boundary.Mars has had a complex history of dynamic evolution, possibly analogous to the more stable regions of Earth. Its geochemical differentiation and thermal regime should account for long-term postaccretional tectonic and volcano-tectonic processes as well as for fluid media on its surface sufficient to cause erosion, including the cutting of large canyons.     

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Zur Klimaschichtung der Tiefseesedimente Im äquatorialen Atlantischen Ozean

Zusammenfassung Genaue Untersuchungen der Foraminiferenfauna in drei Sedimentkernen aus dem Tiefseeboden des äquatorialen Atlantischen Ozeans von der Schwedischen Tiefsee-Expedition an Bord des M. S. Albatroß 1947/48 haben die Ergebnisse über die Schichtung der Tiefseeablagerungen an Hand des Materials von der Deutschen Meteor-Expedition 1925/27 nicht nur bestätigt, sondern in vielen Punkten stark erweitert.Die allgemein übliche stratigraphische Gliederung des jüngeren Quartärs kann in den Tiefseesedimenten des äquatorialen Atlantischen Ozeans durch die Schwankungen der pelagischen Foraminiferenfauna einwandfrei nachgewiesen werden. In alluvialem Material ist das Klimaoptimum (s. Kern 227 auf Abb. 3) deutlich zu erkennen, in den Ablagerungen der letzten Eiszeit (Würm) die Untergliederung in die drei Stadien (WI, II, III) und die dazwischenliegenden Interstadiale möglich. Die Grenze Würmeiszeit/Letztes Interglazial kann klar festgelegt werden (s. Abb. 3), und der 9,09 m lange Kern 227 aus dem Gebiet der Kapverdischen Inseln reicht vielleicht bis in die Sedimente aus dem zweiten Interglazial. Durch die wechselnde Zusammensetzung der pelagischen Foraminiferenfauna sind somit innerhalb der Tiefseeabsätze deutlich die Klimaschwankungen der jüngsten Vergangenheit erkennbar; d. h. die Stratigraphie der jungquartären Tiefseesedimente ist im wesentlichen durch Klimaänderungen bedingt.     

The Quadrennial Ozone Symposium 2016

<正>1.Overview The 2016 Quadrennial Ozone Symposium(QOS-2016)was held on 4–9 September 2016 in Edinburgh,UK.The Symposium was organized by the International Ozone Commission(IO3C),the NERC Centre for EcologyHydrology and the University of Edinburgh,and was co-sponsored by the International Union of Geodesy and Geophysics,the International Association of Meteorology and Atmospheric     

High stress late Maastrichtian – early Danian palaeoenvironment in the Neuquén Basin, Argentina

During the late Maastrichtian to early Danian the Neuquén Basin of Argentina was adjacent to an active volcanic arc to the west and an extensive land area to the northeast. Mineralogical and geochemical studies of the Bajada del Jagüel in the Neuquén Basin indicate a generally warm climate with seasonal changes in humidity and an open seaway to the South Atlantic that maintained marine conditions. Biostratigraphic and quantitative foraminiferal and nannofossil analyses indicate that sediment deposition during the late Maastrichtian (zones CF4-CF2, N. frequens) occurred in relatively shallow middle neritic (100 m) depths with largely dysaerobic bottom waters (abundant low O₂ tolerant benthics) and fluctuating sea level. Calcareous nannofossils indicate a high stress marine environment dominated by Micula decussata. Planktic foraminifera mimic the post-K/T high stress environment with alternating blooms of the disaster opportunists Guembelitria and low oxygen tolerant Heterohelix groups, indicating nutrient-rich surface waters and an oxygen depleted water column. The high stress conditions were probably driven by high nutrient influx due to upwelling and terrestrial and volcanic influx. The K/T boundary is marked by an erosional surface that marks a hiatus at the base of a 15-25 cm thick volcaniclastic sandstone, which contains diverse planktic foraminiferal zone P1c assemblages and nannofossils of zone NP1b immediately above it. This indicates deposition of the sandstone occurred 500 ky after the K/T hiatus. No evidence of the Chicxulub impact or related tsunami deposition was detected.     

Foundations of cable car towers upon alpine glaciers

This paper presents a design approach for strip footings upon glacier ice. Safety against ultimate limit state is proved by the geotechnical slip-line field solution by Prandtl. Glacier ice at 0°C can be modelled as purely cohesive material. Statistical evaluation of uniaxial compression tests with high strain rate revealed a mean value of the cohesion of 600 kPa and a characteristic value c _k = 355 kPa (5% fractile). With a coefficient of variation V _c = 0.3, the partial safety factor turns out to be γ _c = 1.9. An approximate solution for estimating the creep settlement rate is presented to check the serviceability limit state: with the width b of the strip foundation, p the foundation pressure and for ice at 0°C. Experiences on Stubai glacier with grate shaped footings showed that creep settlements occurring per year due to maximum foundation pressures 250 kPa did not influence the operation and the maintenance of the cable cars.     

The dependence on system parameters of strange-mode instabilities in accretion discs

A systematic study of the dependence on disc parameters and input physics, such as opacity and the treatment of convection, of strange-mode instabilities in thin accretion discs, which have been discovered recently, is presented. The instabilities are found to exist for a wide range of parameters, are partly very robust, and their growth rates can reach the dynamical range. Even discs on galactic scales around massive black holes are affected by them. Two groups of instabilities can be distinguished, the first of which is related to the radiation-pressure-dominated part of the disc, and the second to helium/hydrogen ionization. By application of the NAR approximation, both of them can be shown to be of mechanical origin, and the classical κ -mechanism can be excluded as the instability mechanism. A heuristic model for strange-mode instabilities proposed in the context of stellar strange-mode instabilities in luminous stars seems to be applicable to the group associated with dominant radiation pressure.     

Abundance and distribution of ichthyoplankton in Narragansett Bay, Rhode Island, 1989–1990

An ichthyoplankton survey (18 stations in seven sampling sectors) was conducted in Narragansett Bay in 1990 to provide information on abundance, distribution, and seasonal occurrence of eggs and larvae of estuarine fishes, including seasonal migrants. An additional goal was to examine changes in species composition, abundance, and distribution occurring since the last baywide survey in 1972–73. The taxonomic composition of eggs and larvae in 1990 (41 species in 25 families from 684 plankton samples) and in 1972–73 (43 species in 28 families from 6900 samples) was similar. Maximum abundance of fish eggs occurred in June and larvae in July, minimum abundance in September to February. Species diversity was greatest in May–July and lowest during January in both surveys. However, egg and larval densities in 1990 were considerably lower than in 1972–73. Bay anchovy, tautog, and cunner accounted for 86% of the eggs and 87% of the larvae in the bay in 1990. These three species accounted for only 55% of the eggs and 51% of the larvae in 1972–73, with menhaden accounting for another 18% of the eggs and 34% of the larvae. Searobins, scup, and butterfish eggs were common in 1973 (19%) but rare in 1990 (2%). Ichthyoplankton abundance for several of the most abundant species was significantly lower (p<0.05) in the Providence River, upper bay, and Greenwich Bay in 1990 than in 1972–73. Density of fish eggs and larvae in the lower portions of the bay was lower in 1990 for some species but not others. Distribution data suggested a general down-bay shift in density in 1990. *** DIRECT SUPPORT *** A01BY085 00015