Thermochronometry and palaeomagnetism of the Archaean Nelshoogte Pluton, South Africa

²⁰⁷Pb/²⁰⁶Pb single-grain zircon, ⁴⁰Ar/³⁹Ar single-grain hornblende and biotite, and ⁴⁰Ar/³⁹Ar bulk-sample muscovite and biotite ages from the Nelshoogte trondhjemite pluton located in eastern Transvaal, South Africa, show that this granitoid had a protracted thermal history spanning 3213±4  Ma to about 3000  Ma. Whole-rock ⁴⁰Ar/³⁹Ar ages from cross-cutting dolerite dykes indicate that these were intruded at about 1900  Ma. There is no evidence of this or other, later events significantly affecting the argon systematics of the minerals from the pluton dated by the ⁴⁰Ar/³⁹Ar method.
  The pluton has a well-defined palaeomagnetic pole which is dated at 3179±18 (2 σ ) Ma by ⁴⁰Ar/³⁹Ar dating of hornblende. This pole (18°N, 310°E, A ₉₅=9°) yields a palaeolatitude of 0°, significantly different from other Archaean poles from the Kaapvaal Craton. The palaeolatitude difference implies that there was significant apparent polar wander during the Archaean. A second, overprinting magnetization seen in the pluton is also seen in the lower-Proterozoic dolerite dykes, and is consistent with other lower-Proterozoic (2150–1950  Ma) poles for southern Africa.     

Intermediate-term periodicities in the green corona brightness of the Sun

We have analysed intermediate-term periodicities in the green corona by dividing 10° latitudinal belts for the solar cycles 18, 19, and 20 (1947–1976). Discrete Fourier transform technique was used and three noticeable periodicities (3.48, 2.57, and 2.27 years) were found. The physical origin of these periods is not known, but evidence in our results exclude the possibility that the observed periods are a harmonic due to the method of analyse. The period of 3.48-year is the strongest one. 17.6-month periodicity was found only on around +40° belt while 155-day periodicity was not found in our analysis.     

A reply to Richard Greenberg's review of interplanetary encounters: Close range gravitational interactions

The large-scale dynamics of the Martian winter atmosphere are analyzed and discussed. Results obtained from a baroclinic instability analysis, including a Newtonian radiational damping term, are compared with the Mariner 9 data. The beta plane baroclinic poleward heat fluxes are contrasted with those produced using spherical geometry, from the stationary orographically forced long waves.     

The missing planet

Ovenden's hypothesis suggesting former existence of a planet of 90 Earth masses which supposedly filled the Titius-Bode gap in the asteroid belt and then suddenly disappeared 16 million years ago, is critically examined by the morphological method. It is shown that an explosive removal, however improbable, could have led to the formation of the asteroids from a non-explosive core (the nuclear charge being placed outside of it), but that life on Earth would have been completely destroyed by three successive blasts-one from the direct impact of the ejecta of the planet, another from the increased radiation suddenly emitted by the Sun when hit by the ejecta, and a third one (arriving, however, first) from the radiation emitted by the nuclear explosion. The geological record of the continuity of Life on Earth for the past 10⁹ years definitely excludes the possibility of such an explosion in the late Tertiary.The other mode of removal of the planet-in a gravitational encounter with an intruder either from interstellar space or from the unexplored outskirts of the solar system, under the condition of not having disturbed the existing regularity of planetary orbits-is not only extremely improbable, to be expected once during 100 million times the age of the solar system; but it would leave no asteroids behind, all of the previously existing primaeval asteroids having been rapidly eliminated in encounters with the hypothetical planet.Whatever the merits of Ovenden's long-range calculations of the secular perturbations of coplanar circularized planetary orbits, the hypothesis of a massive planet to have existed in the asteroidal region and then recently to have suddenly disappeared, belongs to the realm of the impossible. After such a hypothetical event, either we would not be here on Earth, or there would be no asteroids in their present place between Jupiter and Mars.Paper dedicated to Professor Hannes Alfvén on the occasion of his 70th birthday, 30 May 1978.     

The Atmospheric Boundary Layer Over Baltic Sea Ice

A new parametrization for the surface energy balance of urban areas is presented. It is shown that this new method can represent some of the important urban phenomena, such as an urban heat island and the occurrence of a near-neutral nocturnal boundary layer with associated positive turbulent heat fluxes, unlike the traditional method for representing urban areas within operational numerical weather prediction (NWP) models. The basis of the new parametrization is simple and can be applied easily within an operational NWP model. Also, it has no additional computational expense compared to the traditional scheme and is hence applicable for operational forecasting requirements. The results show that the errors for London within the Met Office operational mesoscale model have been significantly reduced since the new scheme was introduced. The bias and root-mean-square (rms) errors have been approximately halved, with the rms error now similar to the model as a whole. The results also show that a seasonal cycle still exists in the model errors, but it is suggested that this may be caused by anthropogenic heat sources that are neglected in the urban scheme.The British Crowns right to retain a non-exclusive royalty-free license in and to any copyright is acknowledged.     

Measurement and evaluation of the hydrodynamics and secondary currents in and near a strait connecting large water bodies—A field study

The straits connect two large water bodies show highly strong and stratified currents related to meteorological, morphological and hydrodynamic conditions. In some cases, spatial and temporal changes of the stratified currents and their thickness, direction and magnitude are so complex. This complexity directly affects the circulation pattern in the region, water exchange between both ends of the straits and migration of fish species. In order to understand general characteristics of this kind of straits and identifying the complexity of the hydrodynamics of the region and evaluate the secondary currents and recirculation need long term, intensive, field work and measurement studies. As an example of this kind of hydrodynamically complex straits, Bosphorus strait is selected for a field study. The Bosphorus strait has a strongly stratified two-layer system and a unique case of the maximal exchange regime typical of strait flows, which is largely determined by conditions at the Black Sea. Although the Bosphorus strait has distinct two-layer stratification with an associated two-layer system exchange, no continuous current measurements have been made so far, previous measurements all having been random sampling.In this paper, a detailed measurement program has been applied to Bosphorus strait. In the measurement program, a short-term current profile measurement at selected locations at southern part of the strait has been conveyed. Additionally a long-term measurement of current profile has been performed at a selected critical location (in front of the Dolmabahçe Palace) where a recirculation flow exists in the strait. The scope of this paper is to present the techniques and the results of analysis of measurement data. In the measurements the current profile (magnitude and direction) has been determined at every 1 m depth intervals from the surface to the sea bottom at 3 min duration at every hour. Measurements provide that lower-layer flows in northward direction from the Sea of Marmara towards the Black Sea, whereas the upper-layer flow comes from the Black Sea and flows towards the Sea of Marmara in the opposite direction of lower layer. The Bosphorus strait exhibits distinctive features associated with variations in its width and depth. The meandering features of Bosphorus also cause recirculation flows. These results of measurements are presented, discussed and compared with previous studies.     

Detecting of Lithological Units by Using Terrestrial Spectral Data and Remote Sensing Image

The objective of the study was to carry out an automatic classification of the lithological units of interest using the integration of remote sensing image, in which various objects are spread on, and terrestrial spectral measurement data. Only endmembers of interest are classified using spectral classification methods such as Spectral Angle Mapper. Following the identification of the types of rock and minerals, integration of remote sensing images and spectral measurement data enable spectral classification. In this study, Short Wave Infrared detector images of Advanced Spaceborne Thermal Emission and Reflection Radiometer satellite and spectroradiometer measurements were used. The study area, Gölova with its geological diversity is located in the Kelkit Valley section of the North Anatolian Fault Zone in Northeast of Turkey. Seventeen rock samples were collected and their coordinates were recorded. The samples were categorized via spectral measurements on their thin sections through petrographic analyses. Marble and Meta lava with different lithological were selected as endmembers. SAM was used as the classification method that enables the analysis of the endmember with the threshold value of 0.009 radian for marble and 0.010 radian for metalava. SAM analysis was compared by visual analysis to principle component analysis, decorrelation stretch, band ratio (R: 4/7, G: 4/1, B (2/3) x (4/3)) and band combination analysis (R: 9, G: 4 and B: 5). This study demonstrates that the SAM method can be successfully used in both the integration of remote sensing image and terrestrial spectral measurement data in lithological classification. Both the endmembers of metalava and marbles were detected in the SAM results at the GPS coordinates noted down whilst collecting the rock samples for accuracy assessment.