The geological and geodynamic evolution of the eastern Black Sea basin: insights from 2-D and 3-D tectonic modelling

Subsidence mechanisms that may have controlled the evolution of the eastern Black Sea have been studied and simulated using a numerical model that integrates structural, thermal, isostatic and surface processes in both two- (2-D) and three-dimensions (3-D). The model enables the forward modelling of extensional basin evolution followed by deformation due to subsequent extensional and compressional events. Seismic data show that the eastern Black Sea has evolved via a sequence of interrelated tectonic events that began with early Tertiary rifting followed by several phases of compression, mainly confined to the edges of the basin. A large magnitude (approximately 12 km) of regional subsidence also occurred in the central basin throughout the Tertiary. Models that simulate the magnitude of observed fault controlled extension (β=1.13) do not reproduce the total depth of the basin. Similarly, the modelling of compressional deformation around the edges of the basin does little to enhance subsidence in the central basin. A modelling approach that quantifies lithosphere extension according to the amount of observed crustal thinning and thickening across the basin provides the closest match to overall subsidence. The modelling also shows that deep crustal and mantle–lithosphere processes can significantly influence the rate and magnitude of syn- to post-rift subsidence and shows that such mechanisms may have played an important role in forming the anomalously thin syn-rift and thick Miocene–Quaternary sequences observed in the basin. It is also suggested that extension of a 40–45 km thick pre-rift crust is required to generate the observed magnitude of total subsidence when considering a realistic bathymetry.     

Geophysical surveys to help map buried igneous intrusions,Snowdonia, North Wales,UK

The geology of the Snowdonia National Park in North Wales comprises a mixture of Lower Palaeozoic shallow marine sediments, acidic igneous rocks and basic intrusions of the Welsh Basin that were subsequently deformed during the Caledonian Orogeny. Thin igneous intrusions are challenging to map due to variable surface exposures, their intrusive origin, structural deformation and burial by glacial sediments. This study used a combination of traditional geological techniques, near‐surface geophysical surveys and remote sensing to detect and map a buried dolerite sheet intrusion. Both simple and mathematical analysis of magnetic anomalies and numerical modelling allowed the dolerite position, depths and target widths to be determined. Results showed that calibrated magnetic surveys can characterize buried igneous bodies in such mountainous environments.     

Ultraviolet complex refractive index of Martian dust: Laboratory measurements of terrestrial analogs

The optical complex index of refraction of four candidate Martian surface materials has been determined between 0.185 and 0.4 μm using a modified Kubelka-Munk scattering theory. The candidate materials were limonite, andesite, montmorillonite, and basalt. The effect of scattering has been removed from the results. Also presented are diffuse reflection and transmission data on these samples.     

Photometric and polarimetric properties of the bruderheim chondritic meteorite

Photometric and polarimetric laboratory measurements were made as a function of phase angle in the U(0.36 μm), G(0.54 μm) and R(0.67 μm) bands for 0°, 30° and 60° incident illumination on four particle size ranges of Bruderheim, an L6 olivine-hypersthene chondritic meteorite. The four particle size ranges were: 0.25–4.76 mm, 0.25–4.76 mm coated with <74 μm powder, 74–250 μm, and <37 μm. In addition, normal reflectance measurements were made in the spectral range from 0.31 to 1.1 μm. Comparison with astronomical data reveals that none of the asteroids in the main belt for which adequate observations exist can be matched with Bruderheim, which is representative of the most common meteoritic material encountered by the Earth. However, it appears from the polarization and photometry data that the surface of the Apollo asteroid Icarus is consistent with an ordinary chondrite composition. This suggests the possibility that this material, although common in Earth-crossing orbits, is rare as a surface constituent in the main asteroid belt.     

A frequency analysis of a newδ Scuti star HR 7439

HR 7439 (HD 184705) is an F0V star which we have discovered to be a low amplitude Scuti star. This star is multi-periodic with frequencies in the range of 17 to 22 d^–1 (periods in the range 65 to 85 min). These periods are relatively short for such a cool star. Calculation of the pulsation constant Q and comparison with models indicates pulsation in the fourth and fifth overtones. Interestingly, an appropriate model calculated by Stellingwerf shows highest growth rates for the fourth and fifth overtones.     

冲绳海槽浮岩的高温高压纵波速度

对采自冲绳海槽中部海底的浮岩样品和邻近陆地樱岛火山的安山岩样品进行了温度 (常温 - 15 0 0℃ )与压力 (常压 - 2 .4 GPa)实验 ,测得在较低温度 -压力条件下 (<1GPa,<80 0℃ )浮岩样品的纵波速度小于安山岩样品的纵波速度 ,在较高温度 -压力条件下 (>1GPa,>80 0℃ )二者的纵波速度接近一致 (5 .9km /s)。 1GPa/80 0℃是浮岩样品和安山岩样品的热动力相变点 ,推测该点的深度大于 18km。     

Polar orbits around binary stars

Oks proposes the existence of a new class of stable planetary orbits around binary stars, in the shape of a helix on a conical surface whose axis of symmetry coincides with the interstellar axis, and rotates with the same orbital frequency as the binary pair. We show that this claim relies on the inappropriate use of an effective potential that is only applicable when the stars are held motionless. We also present numerical evidence that the only planetary orbits whose planes are initially orthogonal to the interstellar axis that remain stable on the time scale of the stellar orbit are ordinary polar orbits around one of the stars, and that the perturbations due to the binary companion do not rotate the plane of the orbit to maintain a fixed relationship with the axis.     

Large-Scale Structure of the Carina Nebula

Observations obtained with the Midcourse Space Experiment (MSX) satellite reveal for the first time the complex mid-infrared morphology of the entire Carina Nebula (NGC 3372). On the largest size scale of approximately 100 pc, the thermal infrared emission from the giant H ii region delineates one coherent structure: a (somewhat distorted) bipolar nebula with the major axis perpendicular to the Galactic plane. The Carina Nebula is usually described as an evolved H ii region that is no longer actively forming stars, clearing away the last vestiges of its natal molecular cloud. However, the MSX observations presented here reveal numerous embedded infrared sources that are good candidates for sites of current star formation. Several compact infrared sources are located at the heads of dust pillars or in dark globules behind ionization fronts. Because their morphology suggests a strong interaction with the peculiar collection of massive stars in the nebula, we speculate that these new infrared sources may be sites of triggered star formation in NGC 3372.     

Salt weathering and experimental desalination treatment of building sandstone,Sydney (Australia)

Local sandstone used in nineteenth century buildings in Sydney has been affected by salt weathering and surface crust formation. This study trialled two approaches, namely washing-and-vacuuming and poulticing, to salt-removal treatment of weathered sandstone blocks from the Sydney Hospital and Australian Museum. Both treatments removed solutes from the stones in laboratory tests. ICP/titration of sampled scrapings at depths of 0–2, 2–5 and >50 mm showed substantial between-sample variation, with no significant difference being recorded in solute levels after treatment (Mann–Whitney U test), except for sulfur and sodium. Sulfur levels increased at the surface (0–2 mm) following washing-and-vacuuming but not poulticing for the Hospital and Museum samples. Sodium levels increased at the surface (0–2 mm) following poulticing but not washing-and-vacuuming for the Hospital samples. The presence of surface crusts may have contributed to some of the variation in desalination responses.     

The rings of saturn: A frost-coated semiconductor?

Optical complex indices of refraction for the iron-sulfur semiconductors troilite and pyrrhotite have been measured between 0.3 and 1.1 μm, and at 1.5 and 3.0 cm in the microwave region. The behavior of the absorptive and refractive components of the index in the visual and ultraviolet regions suggests a reasonable match to published data on Saturn's rings. A combination of the iron sulfur with water ice and the orthopyroxene enstatite is consistent with an equilibrium condensation model for the formation of the solar system; the water ice and an orthopyroxene are also suggested by near-infrared observational data. A combination of these materials could explain all spectral features seen in the ring spectra to date. The microwave behavior of a small quantity of troilite embedded in water ice at low temperatures is consistent with the radar reflectivity and radio emissivity data.