Enigma variations: the stratigraphy,provenance, palaeoseismicity and depositional history of the Lower Old Red Sandstone Cosheston Group,south Pembrokeshire,Wales

The Lower Devonian (Lochkovian‐Emsian) Cosheston Group of south Pembrokeshire is one of the most enigmatic units of the Old Red Sandstone of Wales. It consists of a predominantly green, exceptionally thick succession (up to 1.8 km) within the red c. 3 km‐thick fill of the Anglo‐Welsh Basin, but occupies a very small area (27 km²). Four formations—Llanstadwell (LLF), Mill Bay (MBF), Lawrenny Cliff (LCF) and New Shipping (NSF)—group into lower (LLF + MBF) and upper (LCF + NSF) units on stratigraphical and sedimentological criteria. Two palynostratigraphic associations (Hobbs Point and Burton Cliff) are recognised in the LLF. Overall, the Cosheston succession comprises a fluvial, coarsening‐upward megasequence, mostly arranged in fining‐upward rhythms. It is interpreted as the fill of an east‐west graben bounded by faults to the north and south of the Benton and Ritec faults, respectively. Both ‘lower Cosheston’ formations were deposited by east‐flowing, axial river systems draining a southern Irish Sea landmass. Drainage reversal, early in the deposition of the LCF, resulted in ‘upper Cosheston’ lateral, SW‐flowing rivers which carried predominantly second‐ and multi‐cycle detritus. The ‘lower Cosheston’ is characterized by an abundance of soft‐sediment deformation structures, probably seismically triggered by movements along the graben's northern bounding fault. A minimum average (≥ mesoseismic) earthquake recurrence interval of c. 4000 yr is estimated for the MBF. This and the correlative Senni Formation of south‐central Wales form a regionally extensive green‐bed development that represents a pluvial climatic interval. Copyright © 2006 John Wiley & Sons, Ltd.     

Radar Detection of Near-Earth Asteroids 2062 Aten, 2101 Adonis, 3103 Eger, 4544 Xanthus, and 1992 QN

We describe Doppler-only radar observations of near-Earth asteroids 2062 Aten, 2101 Adonis, 3103 Eger, 4544 Xanthus, and 1992 QN that were obtained at Arecibo and Goldstone between 1984 and 1996. Estimates of the echo spectral bandwidths, radar cross sections, and circular polarization ratios of these objects constrain their pole-on breadths, radar albedos, surface roughnesses, taxonomic classes, rotation periods, and pole directions. Aten's bandwidth is consistent with its radiometrically determined diameter of 0.9 km. Adonis has a rotation periodP≤ 11 h and an effective diameter (the diameter of a sphere with the same projected area as the asteroid) between 0.3 and 0.8 km. The radar properties of Adonis suggest it is not a member of taxonomic classes C or M. The effective diameter of Xanthus is between 0.4 and 2.2 km with a rotation periodP≤ 20 h. Echoes from 1992 QN constrain the asteroid's pole-on breadth to be ≥0.6 km and probably exclude it from the C and M taxonomic classes. The strongest Eger echoes are asymmetric with bandwidths that set lower bounds of 1.5 and 2.3 km on the minimum and maximum breadths of the asteroid's pole-on silhouette. If Eger is modeled as a 1.5 × 2.3 km biaxial ellipsoid, then its effective diameter for an equatorial view is 1.5 km end-on and 1.9 km broadside or pole-on, implying a geometric albedo smaller than published values but still consistent with a classification as an E-type object. The near-unity circular polarization ratios of Adonis, Eger, and 1992 QN are among the highest values measured for any asteroid or comet and suggest extreme near-surface roughness at centimeter to meter scales.     

Sustainability of deep-sea fisheries

As coastal fisheries around the world have collapsed, industrial fishing has spread seaward and deeper in pursuit of the last economically attractive concentrations of fishable biomass. For a seafood-hungry world depending on the oceans' ecosystem services, it is crucial to know whether deep-sea fisheries can be sustainable.The deep sea is by far the largest but least productive part of the oceans, although in very limited places fish biomass can be very high. Most deep-sea fishes have life histories giving them far less population resilience/productivity than shallow-water fishes, and could be fished sustainably only at very low catch rates if population resilience were the sole consideration. But like old-growth trees and great whales, their biomass makes them tempting targets while their low productivity creates strong economic incentive to liquidate their populations rather than exploiting them sustainably (Clark's Law). Many deep-sea fisheries use bottom trawls, which often have high impacts on nontarget fishes (e.g., sharks) and invertebrates (e.g., corals), and can often proceed only because they receive massive government subsidies. The combination of very low target population productivity, nonselective fishing gear, economics that favor population liquidation and a very weak regulatory regime makes deep-sea fisheries unsustainable with very few exceptions. Rather, deep-sea fisheries more closely resemble mining operations that serially eliminate fishable populations and move on.Instead of mining fish from the least-suitable places on Earth, an ecologically and economically preferable strategy would be rebuilding and sustainably fishing resilient populations in the most suitable places, namely shallower and more productive marine ecosystems that are closer to markets.     

Multi-level participation for building adaptive capacity: Formal agency-community interactions in northern Kenya

Multi-level, networked participation is a vital component in building social–ecological resilience and the capacity to adapt to environmental change. This paper outlines the ways in which multi-level participation contributes to adaptive capacity and, in so doing, takes a step toward articulating a theory of participation based on resilience thinking. We use a case study of Gabra pastoralist communities of northern Kenya to illustrate how multi-level participation may lead to increasing adaptive capacity, above and beyond existing pastoralist adaptations. The findings suggest that adaptive capacity is systemic—that is to say, it is a property of the social–ecological system, including especially the network of institutional linkages that characterizes that system, as much as it is a property of particular actors within the system. We argue that there are three key elements of meaningful multi-level participation: an institutional environment in which the various levels of institutions are linked, inclusivity in decision-making at these various levels, and deliberation. These three features can work together to create meaningful multi-level participation, to facilitate the co-production of knowledge and to build adaptive capacity.     

Re--Os and Sm--Nd Isotope Geochemistry of the Stillwater Complex, Montana: Implications for the Petrogenesis of the J-M Reef

Re—Os and Sm—Nd isotopic data have been obtainedfor mafic and ultramafic cumulates from the 2700-Ma StillwaterComplex and associated fine-grained sills and dykes, so as tobetter constrain the geochemical characteristics of Stillwaterparental magmas and to trace the source(s) of the precious metalsthat have been concentrated in the J-M Reef, the major platinum-groupelement mineral deposit in the complex. Initial Os isotopiccompositions (¹⁸⁷Os/¹⁸⁸Os) for chromitites from the Ultramaficseries range from a radiogenic isotopic composition of 0.1321(_Os = +21) for the platinum group element (PGE)-enriched B chromititeseam from the West Fork area to a near-chondritic isotopic compositionof 0.1069–0.1135 (_Os=–2 to +4.1) for the PGE-poorG and H chromitite seams, respectively, near the middle of theUltramafic series. Osmium isotopic data for the PGE-rich B chromititeseam are generally isochronous with whole-rock and mineral datafor the J-M Reef (_Os = + 12 to + 34). Re—Os isotopic datatherefore document a contrast between PGE-poor cumulates fromthe Ultramafic series and PGE-enriched cumulates from both theUltramafic series and the J-M Reef, suggesting that Os and probablythe other PGE were derived from at least two isotopically distinctsources. Moreover, these Re-Os isotopic characteristics correlatewith petrogenetic subdivisions of the Stillwater Complex basedon field mapping, petrology, REE geochemistry, and Sm—Ndisotope geochemistry. The data are best explained by mixingof two magma types, referred to as U-type and A-type magmas,with differing major element, trace element, and precious metalabundances and isotopic compositions. Although crustally contaminatedkomatiites can mimic the Os and Nd isotopic characteristicsof the U-type magma, the combination of low initial Os isotopicvalues (_Os0) with low initial Nd isotopic values (_Nd–1),high ²⁰⁷Pb/²⁰⁴Pb for a given ²⁰⁶Pb/²⁰⁴Pb (Wooden et al., 1991),and high (Ce/Yb)_n ratios in U-type cumulates and fine-grainedsills and dykes is more consistent with the involvement of aRe-poor, but trace-element-enriched portion of the subcontinentallithospheric mantle in the petrogenesis of Stillwater U-typemagmas. However, the radiogenic initial Os isotopic compositionsof the J-M Reef and other portions of the intrusion with elevatedPGE concentrations suggest that A-type parental magmas incorporatedOs from radiogenic early Archaean crust. The relatively largerange in (Ce/Yb)_n, _Os, and _Nd values suggests that mixing ofgeochemically distinct magmas may have been an important processthroughout the history of the Stillwater magma chamber. Magmamixing may then explain not only the PGE-enriched J-M Reef butalso the anomalous enrichment of the PGE in the B chromititeseam from the West Fork area and the variable values observedin other chromitite seams of the Ultramafic series. The intimateassociation of these magma types, derived from or modified inthe Archaean continental lithosphere, may then be crucial tothe formation of magmatic PGE mineral deposits.     

Radar observations of asteroid 1999 JM8

Abstract— We report results of delay‐Doppler observations of 1999 JM8 with the Goldstone 8560 MHz (3.5 cm) and Arecibo 2380 MHz (13 cm) radars over 18 days in July‐August 1999. The images place thousands of pixels on the asteroid and achieve range resolutions as fine as 15 m/pixel. The images reveal an asymmetric, irregularly shaped object with a typical overall dimension within 20% of 7 km. If we assume that 1999 JM8's effective diameter is 7 km, then the absolute magnitude, 15.15, and the average Goldstone radar cross section, 2.49 km², correspond to optical and radar albedos of 0.02 and 0.06, establishing that 1999 JM8 is a dark object at optical and radar wavelengths. The asteroid is in a non‐principal axis spin state that, although not yet well determined, has a dominant periodicity of ?7 days. However, images obtained between July 31 and August 9 show apparent regular rotation of features from day to day, suggesting that the rotation state is not far from principal axis rotation. 1999 JM8 has regions of pronounced topographic relief, prominent facets several kilometers in extent, numerous crater‐like features between ?100 m and 1.5 km in diameter, and features whose structural nature is peculiar. Arecibo images provide the strongest evidence to date for a circular polarization ratio feature on any asteroid. Combined optical and radar observations from April 1990 to December 2000 permit computation of planetary close approach times to within ± 10 days over the interval from 293 to at least 2907, one of the longest spans for any potentially hazardous asteroid. Integration of the orbit into the past and future shows close approaches to Earth, Mars, Ceres, and Vesta, but the probability of the object impacting Earth is zero for at least the next nine centuries.     

Persistent organic pollutants (POPs) in killer whales (Orcinus orca) from the Crozet Archipelago, southern Indian Ocean

Persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and dibenzofurans (PCDFs), are ubiquitous environmental contaminants of which significant concentrations are reported in upper trophic level animals. In 1998, we collected blubber biopsy samples (n = 11) from killer whales (Orcinus orca) inhabiting the coastal waters around Possession Island, Crozet Archipelago, southern Indian Ocean, for contaminant analyses. Despite inhabiting an isolated region far removed from industrial activities, these killer whales can presently be considered among the most PCB-contaminated cetaceans in the southern hemisphere, with concentrations ranging from 4.4 to 20.5 mg/kg lipid weight (lw). PCDD levels ranged from below the detection limit (5 ng/kg) to 77.1 ng/kg lw and PCDF levels from below the detection limit (7 ng/kg) to 36.1 ng/kg lw. Over 70% of our study animals had PCB concentrations which exceeded a 1.3 mg/kg PCB threshold established for endocrine disruption and immunotoxicity in free-ranging harbour seals, suggesting that organic contaminants cannot be ruled out as an additional threat to this declining population.     

UBV-Beobachtungen des δ Scuti Sterns HD 181333

Dcr δ Scuti Stem HD 181 333 wurde im Sommer 1979 in drei NHchten mit dem Z\villi, ngstelrskop im irbu-System beobachtet. Es konnte eine Periode von 0.1277 Tagen bestimmt werden. The δ Scuti star HD 181 333 was observed in summer 1979 during thrce nights with the twin telescope in rrbu-system. A period of 0.1277 days was found.     

Decoupling of the Sm-Nd and Re-Os Isotopic Systems in Sulphide-Saturated Magmas in the Halls Creek Orogen, Western Australia

We have observed apparent decoupling of the Re–Os andSm–Nd isotopic systems in sulphide-saturated magmas thatsuggests that bulk two-component or assimilation–fractionalcrystallization (AFC) mixing modelling, based on Re–Osisotopic data, is inappropriate for chalcophile isotopic systemsin turbulent sulphide-saturated magmas. This behaviour is observedin three Palaeoproterozic layered mafic–ultramafic intrusionsin the Halls Creek Orogen of Western Australia. All intrusionsclearly have a basaltic parental magma based on primitive olivineand spinel compositions. The intrusions are light rare earthelement enriched and define a narrow range of initial Nd-isotopicsignatures (