Comparison of Fry strain ellipse and AMS ellipsoid trends to tectonic fabric trends in very low-strain sandstone of the Appalachian fold–thrust belt

In moderately to highly strained sandstones, both the long axis of the bedding-parallel finite-strain ellipse, as calculated by the normalized Fry method, and the projection of the long axis of the AMS ellipsoid on the plane of bedding, align well with local “structural grain” (trends of cleavage, folds, and faults). This relationship implies that results of both 2D Fry and AMS analyses represent the local layer-parallel tectonic strain component. Do both methods provide comparable results for very low-strain sandstone (e.g., <5%)? To address this question, Fry and AMS analyses were conducted in very low-strain sandstone from two localities in the Appalachian foreland fold–thrust belt: near Rosendale in New York and the Lackawanna synclinorium of Pennsylvania. We compared the map projections of both bedding-parallel Fry ellipses and AMS ellipsoids to the local structural grain. In both study areas, projections of the long axis of Fry strain ellipses do not cluster in a direction parallel to structural grain, whereas the projection of the long axes of AMS ellipsoids do cluster closely to structural grain. This observation implies that in very low-strain sandstone, AMS analysis provides a more sensitive “quick” indicator of tectonic fabric than does normalized Fry analysis.     

Grazing itineraries and forage selection of goats in the Al Jabal al Akhdar mountain range of northern Oman

In view of the repeatedly reported overstocking of the high-altitude pastures on Al Jabal al Akhdar, northern Oman, plant species abundance, cover and frequency, and herbaceous mass yield were studied in ungrazed versus heavily grazed areas of this mountain range. In addition, plant species selection by goats along a gradient of 1000–2000 m and spatial extent of pasture areas were investigated after abundant rainfall and a subsequent 6-months dry spell by means of manual observation and GPS/GIS tools.The substantially higher species diversity and herbaceous mass yield in the ungrazed area illustrate the production potential of these mountain pastures or, respectively, the biodiversity and productivity loss resulting from continuous grazing. The concentration of goats' selection on only a dozen herbaceous and ligneous species favours pasture encroachment with poisonous shrubs such as Nerium mascatense in the lower and Dodonaea viscosa in the higher altitudes. Given the spatially limited extent of pasture areas, these are exposed to high stocking rates. Therefore, grazing and feeding schemes need to be developed which reduce livestock pressure on the pastures, taking into account local property rights, herding skills and the recovery potential of the vegetation, which heavily depends on unpredictable rainfall events.     

Distribution and migration of pesticide residues in mosquito control impoundments St. Lucie County, Florida, USA

This project was designed to: (1) document the distribution and migration of organochlorine pesticide residues within marsh substrates of 18 St. Lucie County mosquito control impoundments located along the Indian River Lagoon estuary, and (2) evaluate the impact of water management techniques on residue mobility. Our results indicate that detectible concentrations of organochlorine compounds, applied between the late 1940s and early 1950s, are present in 16 of the 18 St. Lucie County mosquito control impoundments. These compounds are primarily restricted to the surficial, organic-rich wetland sediment, which, based upon geotechnical analysis, was exposed to the atmosphere at a time when the impoundments were subjected to pesticide treatment. Contaminated sediments are present below the surficial, organic-rich layer, suggesting that some vertical migration of pesticides has occurred. It is unlikely that leaching associated with the downward percolation of impounded water was responsible for this migration as pesticide residues were never detected within thein situ pore waters. An alternative explanation is that biological processes (e.g., rooting, burrowing) facilitated the downward flux of organochlorine compounds into sediment horizons not subjected to direct treatment. Eighty-eight surface water samples obtained from two impoundments subjected to contrasting water management techniques were analyzed for pesticide content. None of the surficial water samples collected in association with these impoundments contained detectible concentrations of organochlorine compounds. These samples were unfiltered and contained as much as 25 mg/1 of particulate organic matter. This suggests that the currently preferred management technique (RIM), which is designed to maintain water quality, limit mosquito production, and provide for ecological continuity, does not hydraulically mobilize pesticide residues into the Indian River Lagoon estuary.     

Geology of the Continental Margin of Enderby and Mac. Robertson Lands, East Antarctica: Insights from a Regional Data Set

In 2001 and 2002, Australia acquired an integrated geophysical data set over the deep-water continental margin of East Antarctica from west of Enderby Land to offshore from Prydz Bay. The data include approximately 7700 km of high-quality, deep-seismic data with coincident gravity, magnetic and bathymetry data, and 37 non-reversed refraction stations using expendable sonobuoys. Integration of these data with similar quality data recorded by Japan in 1999 allows a new regional interpretation of this sector of the Antarctic margin. This part of the Antarctic continental margin formed during the breakup of the eastern margin of India and East Antarctica, which culminated with the onset of seafloor spreading in the Valanginian. The geology of the Antarctic margin and the adjacent oceanic crust can be divided into distinct east and west sectors by an interpreted crustal boundary at approximately 58° E. Across this boundary, the continent–ocean boundary (COB), defined as the inboard edge of unequivocal oceanic crust, steps outboard from west to east by about 100 km. Structure in the sector west of 58° E is largely controlled by the mixed rift-transform setting. The edge of the onshore Archaean–Proterozoic Napier Complex is downfaulted oceanwards near the shelf edge by at least 6 km and these rocks are interpreted to underlie a rift basin beneath the continental slope. The thickness of rift and pre-rift rocks cannot be accurately determined with the available data, but they appear to be relatively thin. The margin is overlain by a blanket of post-rift sedimentary rocks that are up to 6 km thick beneath the lower continental slope. The COB in this sector is interpreted from the seismic reflection data and potential field modelling to coincide with the base of a basement depression at 8.0–8.5 s two-way time, approximately 170 km oceanwards of the shelf-edge bounding fault system. Oceanic crust in this sector is highly variable in character, from rugged with a relief of more than 1 km over distances of 10–20 km, to rugose with low-amplitude relief set on a long-wavelength undulating basement. The crustal velocity profile appears unusual, with velocities of 7.6–7.95 km s⁻¹ being recorded at several stations at a depth that gives a thickness of crust of only 4 km. If these velocities are from mantle, then the thin crust may be due to the presence of fracture zones. Alternatively, the velocities may be coming from a lower crust that has been heavily altered by the intrusion of mantle rocks. The sector east of 58° E has formed in a normal rifted margin setting, with complexities in the east from the underlying structure of the N–S trending Palaeozoic Lambert Graben. The Napier Complex is downfaulted to depths of 8–10 km beneath the upper continental slope, and the margin rift basin is more than 300 km wide. As in the western sector, the rift-stage rocks are probably relatively thin. This part of the margin is blanketed by post-rift sediments that are up to about 8 km thick. The interpreted COB in the eastern sector is the most prominent boundary in deep water, and typically coincides with a prominent oceanwards step-up in the basement level of up to 1 km. As in the west, the interpretation of this boundary is supported by potential field modelling. The oceanic crust adjacent to the COB in this sector has a highly distinctive character, commonly with (1) a smooth upper surface underlain by short, seaward-dipping flows; (2) a transparent upper crustal layer; (3) a lower crust dominated by dipping high-amplitude reflections that probably reflect intruded or altered shears; (4) a strong reflection Moho, confirmed by seismic refraction modelling; and (5) prominent landward-dipping upper mantle reflections on several adjacent lines. A similar style of oceanic crust is also found in contemporaneous ocean basins that developed between Greater India and Australia–Antarctica west of Bruce Rise on the Antarctic margin, and along the Cuvier margin of northwest Australia.     

Diffuse cosmic gamma-ray background in the 28 ke V-4.1 MeV range from Kosmos 461 observations

Diffuse cosmic background and atmospheric gamma-radiation in the range 28 keV-4.1 MeV were studied with a scintillation spectrometer on board of the Kosmos 461 satellite. Separation of the cosmic and atmospheric components was made possible through a reliable determination of the geomagnetic dependences of albedo gamma-radiation: The spectrum of diffuse background in the energy range covered cannot be fitted with a common law. At energies below 400 keV the spectrum follows a power-law $$I = (5.6 \pm 0.5) \times 10^{ - 3} E^{ - (2.80 \pm 0.05)} cm^{ - 2} s^{ - 1} sr^{ - 1} MeV^{ - 1} .$$ Starting from 400 keV, this power-law breaks down; the spectrum revealing a clearly pronounced shoulder. Extrapolation of the power-law spectrum to higher energies shows that the gamma-ray component responsible for the change in the shape of the spectrum is quite strong, becoming predominant in the diffuse background in the range 1–100 MeV. The intensity of excess radiation is maximum in the region of 700–800 keV reaching ～1.8×10^?2 cm^?2s^?1sr^?1 MeV^?1. The shape of the high energy component spectrum of the diffuse background constructed using the data of Kosmos 461 and SAS-2 is in agreement with the hypotheses of the cosmological origin of the radiation.     

Paleogeography and paleomagnetism of the Nubian Sandstone Eastern Desert of Egypt

The present work gives the results of the paleomagnetic investigations carried out on the Cretaceous Nubian Sandstone and associated volcanics and hematitic oolitic iron ores in the Eastern Desert of Egypt. The paleogeography of the Nubian Sandstone especially for the Eastern Desert is discussed in the light of the various geological data as well as the paleomagnetic results, both of which point to certain conceptions. The position of the paleoequator and paleolatitude 20° S were derived from the paleomagnetic data indicating that the Nubian Sandstone was originally deposited in the paleoequatorial to subequatorial zone. The paleomagnetic results corroborate previous African data that there has been no polar wandering and continental drift for Africa during 210 to 110 million years and extend this period to 85 million years.It is concluded that the Nubian Sandstone is deposited under tropical to subtropical climate and that it is formed under various continental conditions excluding eolian merging intermittently into shallow marine.

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Zusammenfassung Die vorliegende Arbeit ist das Ergebnis paläomagnetischer Untersuchungen, die in kretazischer Nubischer Serie und zugehörigen vulkanischen Gesteinen sowie in hämatitischoolithischen Eisenerzen in der östlichen Wüste in Ägypten durchgeführt wurden. Es wird die Paläogeographie der Nubischen Serie, besonders der östlichen Wüste, diskutiert, einmal anhand verschiedener geologischer Beobachtungen und darüber hinaus anhand der paläomagnetischen Daten; beides weist auf ähnliche Deutungen hin. Die Lage des Paläoäquators und des Paläobreitenkreises 20° S zeigt an, daß die Nubische Serie in der Umgebung des damaligen Äquators abgelagert wurde. Die paläomagnetischen Ergebnisse bestätigen frühere afrikanische Daten, nach denen keine Kontinentaldrift für diesen Raum zwischen 210 und 110 Mill. Jahren stattfand, und erweitern diese Periode bis 85 Mill. Jahre. Es wird angenommen, daß die Nubische Serie in tropischem bis subtropischem Klima abgelagert wurde, und zwar unter den verschiedensten kontinentalen Ablagerungsbedingungen.

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Résumé Le présent travail est le résultat des recherches paléomagnétiques effectuées sur le grès nubien crétacé, les volcanites associées et les minerais de fer hématitiques et oolithiques dans le désert oriental de l'Egypte. La paléogéographie du grès nubien, surtout celui du désert oriental, est discutée à la lumière des différentes observations géologiques variées et, en outre, des données paléomagnétiques; toutes deux concluent a la même signification. La position du paléoéquateur et de la paléolatitude 20° S montre que la série nubienne a été déposée dans le domaine proche de l'équateur relatif à cette époque.Les résultats paléomagnétiques corroborent les données africaines antérieures d'après lesquelles il n'y aurait pas eu, pour ces régions, de dérive continentale entre 210 à 110 millions d'années; ils prorogent cette période jusqu'à 85 millions d'années.On admet que le grès nbien fut déposé sous le climat tropical à sub-tropical et effectivement sous les différentes conditions de dépôt continentales.

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