Utilization of ASTER and OLI data for lithological mapping of Nugrus-Hafafit area,South Eastern Desert of Egypt

Lithological discrimination of Neoproterozoic rocks occupying Nugrus-Hafafit area, South Eastern Desert of Egypt, has been carried out using Operational Land Imager (OLI) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensors’ imagery data. The applicable processing enhancement techniques include optimum index factor (OIF), band ratioing, principal component analysis (PCA), and minimum noise fraction (MNF) transform. The area comprises varieties of low-grade metamorphosed ophiolitic mélange and island-arc rocks, thrusting over high-grade metamorphic gneissic core complexes, and intruded by syn-, late-, and post-tectonic granitoids. The OLI band ratio 6/7 discriminates clearly the ophiolitic serpentinites-talc-carbonate rocks, while 4/5 ratio image is able to separate between mafic and felsic rocks. Moreover, the ASTER band ratio 6/8 is used to distinguish the amphibole-bearing rocks, including amphibolite and hornblende gneiss. The OLI and ASTER second principal component (PC2) images reflect the contrast spectral behavior of ophiolitic mélange rocks through visible-near-infrared (VNIR) and shortwave (SWIR) regions. The OLI-PC3 shows the ability to delineate the Fe-rich rocks, including amphibolite and metamafics, while ASTER-PC3 is effective for quartz-feldspathic granites and psammitic gneisses. Visual interpretation and integration of processed data with petrography and field investigation resulted in complete differentiation for the different lithologies and creation of a new detailed geological map of Nugrus-Hafafit area.     

Stratigraphic and geochronological context of human habitation along the Galana River,Kenya

Geoarchaeological investigations along the Galana River, eastern Kenya, document a pattern of channel aggradation and then degradation from the Middle to Late Holocene. Archaeological occupations at six sites in fluvial terraces along a ˜100 km stretch of the Galana River in Tsavo East National Park correspond with fluvial aggradation beginning ca. 6000 years ago. Artifact analyses indicate that the inhabitants of these sites utilized ceramics and stone tools similar to Pastoral Neolithic traditions detected at other penecontemporaneous archaeological sites in East Africa and possessed domesticated cattle from ca. 3700 years ago. The site occupations that occur during this period have dense artifact concentrations of predominantly locally procured items. The Galana River incised after ca. 900 years ago and there is a noticeable paucity of archaeological material, reflecting more peripatetic lifestyles. This shift in settlement pattern may reflect a decrease in reliance on riverine food sources during the Late Holocene, with diminished riparian environments associated with channel incision. © 2007 Wiley Periodicals, Inc.     

Modelling the stress-strain behaviour of saturated rocks undergoing triaxial deformation using complex electrical conductivity measurements

Measurement of complex electrical conductivity as a function of frequency is an extremely sensitive probe for changes in pore and crack volume, crack connectivity, and crack surface topography. Such measurements have been made as a function of pore fluid chemistry, hydrostatic confining pressure, as well as uniaxial and triaxial deformation. This paper will; (1) describe the effects of triaxial deformation on the complex electrical conductivity of saturated porous rocks, (2) use the electrical data to model the mechanical stress-strain behaviour, and (3) compare the modelled behaviour with the stress-strain behaviour measured during the deformation. Experimental conductivity data tracks how the rock undergoes compaction with progressive loss of crack volume, followed by dilatation due to new crack formation, growth of existing cracks, crack interlinkage, and finally failure, as axial strain is increased. We have used the complex electrical data to produce a direction-sensitive (anisotropic) crack damage parameter, and used it to calculate the effective Young's modulus by employing the models of Walsh and Bruner. Comparison of the synthetic stress-strain curves so produced, with the experimentally derived stress-strain curves shows good agreement, particularly for undrained tests. This modelling is an improvement on similar curves produced using isotropic crack damage parameters derived from acoustic emission data. The improvement is likely to be due to the directional sensitivity of the electrical conductivity measurement, and its ability to discriminate between the formation of isolated cracks, and those cracks that contribute to the inter-connected crack space i.e. those cracks upon which transport properties of the rock such as electrical conductivity, and mechanical properties depend most critically during triaxial deformation.     

Continuation of the San Andreas fault system into the upper mantle: Evidence from spinel peridotite xenoliths in the Coyote Lake basalt, central California

The Coyote Lake basalt, located near the intersection of the Hayward and Calaveras faults in central California, contains spinel peridotite xenoliths from the mantle beneath the San Andreas fault system. Six upper mantle xenoliths were studied in detail by a combination of petrologic techniques. Temperature estimates, obtained from three two-pyroxene geothermometers and the Al-in-orthopyroxene geothermometer, indicate that the xenoliths equilibrated at 970–1100 °C. A thermal model was used to estimate the corresponding depth of equilibration for these xenoliths, resulting in depths between 38 and 43 km. The lattice preferred orientation of olivine measured in five of the xenolith samples show strong point distributions of olivine crystallographic axes suggesting that fabrics formed under high-temperature conditions. Calculated seismic anisotropy values indicate an average shear wave anisotropy of 6%, higher than the anisotropy calculated from xenoliths from other tectonic environments. Using this value, the anisotropic layer responsible for fault-parallel shear wave splitting in central California is less than 100 km thick. The strong fabric preserved in the xenoliths suggests that a mantle shear zone exists below the Calaveras fault to a depth of at least 40 km, and combining xenolith petrofabrics with shear wave splitting studies helps distinguish between different models for deformation at depth beneath the San Andrea fault system.     

Boundary crossing and non‐linear theory in earth‐system sciences – a proof of concept based on tsunami and post‐eruption scenarios on Java Island,Indonesia

Although volcanic eruptions are well‐known to be the trigger of some weather and climatic changes, land‐cover changes by pyroclastic‐flows and lahars do not get this recognition, neither do major hazards such as tsunami. These two earth processes are even lesser considered as being able to modify other earth processes they are not directly connected to, such as landslides or river discharge in non‐connected basins more than a hundred kilometres away. In this contribution the authors argue that these ideas are mainly driven by the process of being ‘educated’ in a single academic discipline and once put to the test interactions and retroactions between earth processes and atmospheric processes are far more reaching than commonly thought. For this study, the site of Java Island (Indonesia) was chosen to conduct (1) an analysis of a major tsunami impact – in the same area as the 2006 Java tsunami and (2) an analysis of the post‐eruption impacts of Merapi Volcano after a major eruption – excluding any ejecta in the atmosphere for the sake of the demonstration. The atmospheric feedback simulations were conducted using the regional climate model (RegCM‐4) with calibration from weather stations in Java Island. As a result, both simulations have proven that large scale deposits of pyroclasts (not introducing the ejectas sent in the atmosphere) and tsunamis can have outstanding impacts on the atmospheric situation and the bio‐geomorphologic evolution of the landscape in the following weeks to months. Interestingly enough these impacts are not limited to the area impacted by the earth process and the effect are not linear in time as they work following thresholds. These rainfalls ‘tele‐impacts’ are important enough to, in turn, modify earth‐surface processes in areas remote from the original phenomenon. This system acts in the same manner as a famous butterfly in Africa that could trigger a hurricane on the other side of the Atlantic Ocean. Copyright © 2012 John Wiley & Sons, Ltd.     

Transition probabilities and dissociation energy of astrophysical molecule CoH

The Franck-Condon (FC) factors (transition probabilities) and r-centroids have been evaluated by the reliable numerical integration procedure for the bands of the A ³ φ₄ →X ³ φ₄ system of astrophysical molecule CoH, using a suitable potential. The dissociation energy D ⁰ ₀ = 2.5 ± 0.05 eV for the electronic ground state of CoH has been estimated by fitting Hulburt-Hirschfelder function to the experimental potential energy curve, using the correlation coefficient. This revised version was published online in July 2006 with corrections to the Cover Date.     

Channel change,bankfull and effective discharges on a vertically accreting,meandering, gravel‐bed river

Along the lower reaches of the Waipaoa River, New Zealand, cross‐section survey data indicate there was a 23 per cent decrease in bankfull width and a 22 per cent reduction in channel cross‐section area between 1948 and 2000, as the channel responded to increased inputs of fine (suspended) sediment following deforestation of the headwaters in late C19 and early C20. We determined the bankfull discharge within a ～39 km long reach by routing known discharges through the one‐dimensional MIKE 11 flow model. The model runs suggest that the bankfull discharge varies between ～800 and ～2300 m³ s^?1 and that the average recurrence interval is 4 ± 2 years on the annual maximum series; by contrast, the effective flow (360 m³ s^?1) is equaled or exceeded three times a year. The variability in bankfull discharge arises because the banks tend to be lower in places where flood flows are constricted than in reaches where overbank flow is dispersed over a wide area, and because scour has counteracted aggradation in some locations. There is no downstream variation in Shields stress, or in relative shear stress, within the study reach. Bankfull shear stress is, on average, five times greater than the shear stress required to initiate motion. At the effective discharge it is more than twice the threshold value. The effective discharge probably has more relevance than the bankfull discharge to the overall picture of sediment movement in the lower reaches of the Waipaoa River but, because width is constrained by the stability and resistance of the bank material to erosion during high flows that also scour the bed, the overall channel geometry is likely determined by discharges at or near bankfull. Copyright © 2006 John Wiley & Sons, Ltd.     

The motion of a satellite in an axi-symmetric gravitational field

The equations for the variation of the osculating elements of a satellite moving in an axi-symmetric gravitational field are integrated to yield the complete first-order perturbations for the elements of the orbit. The expressions obtained include the effects produced by the second to eighth spherical harmonics. The orbital elements are presented in the most general form of summations by means of Hansen coefficients. Due to their general forms it is a simple matter to estimate the perturbations of any higher harmonic by simply increasing the index of summation. Finally, this paper gives the respective general expressions for the secular perturbations of the orbital elements. The formulae presented should be useful for the reductions of Earth-satellite observations and geopotential studies based on them.List of Symbols semi-major axis - C _jk ⁿ (, ) cosine functions of and - e eccentricity of the orbit - f acceleration vector of perturbing force - f sin²t - i inclination of the orbit - J _n coefficients in the potential expansion - M mean anomaly - n mean motion - p semi-latus rectum of the orbit - R, S, andW components of the perturbing acceleration - r radius-vector of satellite - r magnitude ofr - S _jk ⁿ (, ) sine functions of and - T time of perigee passage - u argument of latitude - U gravitational potential - true anomaly - V perturbing potential - G(M₊+m) (gravitational constant times the sum of the masses of Earth and satellite) - _n,k coefficients ofR component of disturbing acceleration (funtions off) - _n,k coefficients ofS andW components of disturbing acceleration (functions off) - mean anomaly at timet=0 - X ₀ ^n,m zero-order Hansen coefficients - argument of perigee - right ascension of the ascending node