Shock metamorphism of quartz at the submarine Mjølnir impact crater,Barents Sea

Abstract— Shock metamorphosed quartz grains have been discovered in a drill core from the central peak of the Late Jurassic, marine Mjølnir structure; this finding further corroborates the impact origin of Mjølnir. The intersected strata represent the Upper Jurassic Hekkingen Formation and underlying Jurassic and Upper Triassic formations. The appearance, orientation, and origin of shock features in quartz grains and their stratigraphic distribution within the core units have been studied by optical and transmission electron microscopy. The quartz grains contain planar fractures (PFs), planar deformation features (PDFs), and mechanical Brazil twins. The formation of PFs is the predominant shock effect and is attributed to the large impedance differences between the water‐rich pores and constituent minerals in target sediments. This situation may have strengthened tensional/extensional and shear movements during shock compression and decompression. The combination of various shock effects indicates possible shock pressures between 5 and at least 20 GPa for three core units with a total thickness of 86 m (from 74.00 m to 171.09 m core depth). Crater‐fill material from the lower part of the core typically shows the least pressures, whereas the uppermost part of the allochthonous crater deposits displays the highest pressures. The orientations of PFs in studied quartz grains seem to become more diverse as the pressure rises from predominantly (0001) PFs to a combination of (0001), , and orientations. However, the lack of experimental data on porous sedimentary rocks does not allow us to further constrain the shock conditions on the basis of PF orientations.     

Carbon — From Space to Laboratory

In this review, the nature of carbon-containing molecules and carbonaceous solids present in meteorites, comets, and the interstellar medium is discussed. Carbon plays an active role in the lifecycle of stars and the interstellar medium. It is the basis of a rich interstellar chemistry and the main component of pre-biotic organic material in space. The aim of the review is to build a bridge between astronomical spectroscopy and laboratory studies relevant to the investigation of cosmic carbon. Special emphasis is given to the structural variety of carbon-containing species and their characterization by experimental techniques. This revised version was published online in July 2006 with corrections to the Cover Date.     

Alaska in den Jahren 1911, 1912

Ohne Zusammenfassung     

Übersicht der Veröffentlichungen der U. S. Geological Survey von Januar bis Oktober 1910

Ohne Zusammenfassung     

Der Geologische Atlas der Vereinigten Staaten von Nord-Amerika

Ohne Zusammenfassung     

Past glacial and interglacial conditions in the Arctic Ocean and marginal seas – a review

Past changes in the Arctic Ocean and its marginal seas have been profound, even during the last 10,000 years. Understanding these changes, such as those occurring during the transition from glacial to interglacial climates, are important for research on modern processes, because this knowledge provides a framework and unique perspective in which to view the modern physical and biological processes. This paper discusses our current understanding of past environmental change and processes relative to those currently in progress. Special emphasis is placed on the most recent transition from a glacial state to the modern interglacial conditions.     

Metamorphosis of Heteroxenia fuscescens planulae (Cnidaria: octocorallia) is inhibited by crude oil: a novel short term toxicity bioassay

By using TPA (12-tetra-decanoyl-phorbol-13-acetate) an artificial inducer for metamorphosis, it was possible to determine the effect of crude oil on settlement and metamorphosis of planulae of the soft coral Heteroxenia fuscescens. In the absence of crude oil, TPA induced metamorphosis in 97% of these planulae. The effect of crude oil on metamorphosis and appearance of deformed primary polyps was concentration dependent. Only 50% of the planulae grown in experimental vessels with crude oil at a concentration of 0.1 ppm covering the bottom and walls of the vessels underwent metamorphosis when triggered by TPA. Of those planulae exposed to 100 ppm of the pollutant only 3% metamorphosed after being induced by TPA. Furthermore, oil film on the water surface was less toxic to the larvae than the crude oil covering the bottom and walls of the experimental vessels. Some of the oil treated planulae died, while others remained viable, looked normal, but did not metamorphose after being presented with TPA. These findings suggest that even at very low concentrations crude oil affects larvae of H. fuscescens preventing their settlement and metamorphosis. Therefore it is possible that oil spills affect coral recruitment by decreasing the viability and the settlement of coral planulae. This assay represents a new sensitive bioindicator to detect the impact of oil pollution on tropical and subtropical marine environments.     

Analysis of the IR and sub-MM emission of four post-AGB stars

The goal of this work is to derive the physical properties of dust envelopes around post-AGB stars by means of radiative transfer calculations. The model spectral energy distributions (SEDs) have been compared with observational data of the post-AGB stars IRAS 10215-5916, 16342-3814, 17150-3224, and 19500-1709 in the wavelength range from 0.4 to 1300µm. The match between our model SEDs and the observational data is very satisfactory. As a result, we have obtained estimates of the inner and outer radii, the density, the temperature, and the mass of the envelopes of the four objects.     

New candidates for objects with a 21 micron feature

We report the preliminary result of studying the nature of objects with a 21µm feature. New candidates are presented and possible carriers of the 21µm feature are discussed.