Physical properties of 4 cores from the Bengal Fan

New stratigraphic and high-resolution seismic data from the Bengal Fan indicate that the world's largest fan shows active growth during the most recent sea-level rise and the recent highstand. This unique phenomenon contradicts common sequence-stratigraphic models, and the sediment preserved provides new insight into the sedimentological response of a fan system to sea-level rise, climatic terminations, and monsoon intensity during the past climatic cycle. We present a detailed dated sequence of turbidite sedimentation based on a core transect perpendicular to the active channel-levee system in the upper mid-fan area. Between the two major terminations 1a (12 800 14C yr B.P.) and 1b (9700 14C yr B.P.), and especially at the end of the Younger Dryas, a 13-km-wide channel built up levees 50 m high. With decreasing sediment supply, continued sea-level rise, and increasing monsoon intensity during the early Holocene, turbidity currents were confined to the channel and gradually filled it. The canyon "Swatch of No Ground," a shelf depocenter that serves as the source for frequent turbidity currents, and the channel-levee system provide the unique opportunity for studying an active highstand system. Many fans showed this behavior only during lowered sea-level.

Petrophysical measurement of ODP Leg 122 and 123 samples (Tables 1, 2)

The capillary-pressure characteristics of 22 samples of lithified post-Paleozoic Indian-Ocean carbonates were compared to published data from older carbonate rocks (lower Paleozoic Hunton Group of Texas and Oklahoma). The Indian-Ocean samples are considerably more porous than are the Paleozoic samples, yet all of the Indian-Ocean samples fit readily into a descriptive petrofacies scheme previously established for the Hunton Group. The Indian-Ocean samples may be assigned to four petrophysical facies (petrofacies) based on the shapes of their capillary-pressure curves, their pore-throat-size distributions, their estimated recovery efficiency values (for nonwetting fluids), and the visual characteristics of their pore systems, as observed with a scanning-electron microscope. Petrofacies assignments for the Indian-Ocean samples are as follows. Petrofacies I includes six samples collected from the coarse basal portions of event deposits (primarily turbidites). These samples have large throats, leptokurtic throat-size distributions, low- to moderate recovery efficiency values, concave cumulative-intrusion capillary-pressure curves, and high porosity values. Petrofacies II includes two sedimentologically dissimilar samples that have medium-size throats, platykurtic throat-size distributions, moderate- to-high recovery efficiency values, gently sloping cumulative-intrusion capillary-pressure curves, and high porosity values. Petrofacies III includes two polymictic sandstones and a skeletal packstone that have small throats, polymodal throat-size distributions, moderate recovery efficiency values, gently sloping cumulative-intrusion capillary-pressure curves, and high porosity values. Petrofacies IV includes 11 samples, mostly recrystallized neritic carbonates, that have small throats, leptokurtic throat-size distributions, high recovery efficiency values, convex cumulative-intrusion capillary-pressure curves, and low porosity values. Comparison of petrofacies assignment to core-, thin-section-, and smear-slide data, and to inferred depositional setting, suggests that pore systems in most samples from Holes 765C and 766A result from primary depositional features, whereas pore systems in samples from Hole 761C and one sample from Hole 765C have been strongly influenced by diagenetic processes. For Hole 761C, prediction of petrophysical parameters should be most successful if based on diagenetic facies patterns. By contrast, the distribution of favorable reservoir facies and of permeability barriers in less highly altered rocks collected from Holes 765C and 766A is related to depositional patterns. Recovery efficiency is inversely related to both porosity and median throat size for the present data set. This relationship is similar to that observed for carbonates of the lower Paleozoic Hunton Group and the Ordovician Ellenburger dolomite, but opposite of that observed for some other ancient carbonates. The coarse deposits of the massive basal units of turbidites are petrophysically distinct and form a coherent petrophysical group (Petrofacies I) with substantial reservoir potential. Two samples assigned to Petrofacies I have extremely large throats (median throat size at least 4 ?m, and at least six times that of any other sample) and therefore high permeability values. These two samples come from thin, coarse turbidites that lack or have poorly developed fine divisions and are interpreted to have been deposited on channeled suprafan lobes in a proximal mid-fan setting. The restriction of extremely high permeability values to a single depositional facies suggests that careful facies mapping of deep-sea fans in a deliberate search for such coarse turbidites could dramatically enhance the success of exploration for aquifers or hydrocarbon reservoirs. Such reservoirs should have substantial vertical heterogeneity. They should have high lateral permeability values but low vertical permeability values, and reservoir sections should include numerous thin units having widely differing petrophysical characteristics.

Magnetic extracts of three gravity cores located at the Ceará Rise, the Mid-Atlantic Ridge and the Sierra Leone Rise

The magnetic microparticle and nanoparticle inventories of marine sediments from equatorial Atlantic sites were investigated by scanning and transmission electron microscopy to classify all present detrital and authigenic magnetic mineral species and to investigate their regional distribution, origin, transport, and preservation. This information is used to establish source-to-sink relations and to constrain environmental magnetic proxy interpretations for this area. Magnetic extracts were prepared from sediments of three supralysoclinal open ocean gravity cores located at the Ceará Rise (GeoB 1523-1; 3°49.9'N/41°37.3'W), the Mid-Atlantic Ridge (GeoB 4313-2; 4°02.8'N/33°26.3'W), and the Sierra Leone Rise (GeoB 2910-1; 4°50.7'N/21°03.2'W). Sediments from two depths corresponding to marine isotope stages 4 and 5.5 were processed. This selection represents glacial and interglacial conditions of sedimentation for the western, central, and eastern equatorial Atlantic and avoids interferences from subsurface and anoxic processes. Crystallographic, elemental, morphological, and granulometric data of more than 2000 magnetic particles were collected by scanning and transmission electron microscopy. On basis of these properties, nine particle classes could be defined: detrital magnetite, titanomagnetite (fragmental and euhedral), titanomagnetite-hemoilmentite intergrowths, silicates with magnetic inclusions, microcrystalline hematite, magnetite spherules, bacterial magnetite, goethite needles, and nanoparticle clusters. Each class can be associated with fluvial, eolian, subaeric, and submarine volcanic, biogenic, or chemogenic sources. Large-scale sedimentation patterns are delineated as well: detrital magnetite is typical of Amazon discharge, fragmental titanomagnetite is a submarine weathering product of mid-ocean ridge basalts, and titanomagnetite-hemoilmenite intergrowths are common magnetic particles in West African dust. This clear regionalization underlines that magnetic petrology is an excellent indicator of source-to-sink relations. Hematite encrustations, magnetic spherules, and nanoparticle clusters were found at all investigated sites, while bacterial magnetite and authigenic hematite were only detected at the more oxic western site. At the eastern site, surface pits and crevices were seen on the crystal faces indicating subtle early diagenetic reductive dissolution. It was observed that paleoclimatic signatures of magnetogranulometric parameters such as the ratio of anhysteretic and isothermal remanent magnetizations can be formed either by mixing of multiple sources with separate, relatively narrow grain size ranges (western site) or by variable sorting of a single source with a broad grain size distribution (eastern site). Hematite, goethite, and possibly ferrihydrite nanoparticles occur in all sediment cores studied and have either high-coercive or superparamagnetic properties depending on their partly ultrafine grain sizes. These two magnetic fractions are generally discussed as separate fractions, but we suggest that they could actually be genetically linked.

An unusual, dwarf new species of Neotropical freshwater stingray, Plesiotrygon nana sp. nov., from the upper and mid Amazon basin: the second species of Plesiotrygon (Chondrichthyes: Potamotrygonidae)

A new species of the relatively poorly known Neotropical freshwater stingray genus Plesiotrygon Rosa, Castello & Thorson, 1987 is described from the main channel and smaller tributaries (Ríos Itaya and Pachitea) of the upper Amazon basin in Peru. The first specimen to be collected, however, was from much farther east in Rio Solimões in 1996, just down-river from Rio Purus (specimen unavailable for this study). Plesiotrygon nana sp. nov., is a very distinctive and unusually small species of freshwater stingray (Potamotrygonidae), described here mostly from three specimens representing different size classes and stages of sexual maturity. Plesiotrygon nana sp. nov., is distinguished from its only congener, P. iwamae Rosa, Castello & Thorson, 1987, by numerous unique features, including: dorsal coloration composed of very fine rosettes or a combination of spots and irregular ocelli; very circular disc and snout; very small and less rhomboidal spiracles; short snout and anterior disc region; narrow mouth and nostrils; denticles on dorsal tail small, scattered, not forming row of enlarged spines; adult and preadult specimens with significantly fewer tooth rows; fewer caudal vertebrae; higher total pectoral radials; very small size, probably not surpassing 250 mm disc length or width, males maturing sexually at around 180 mm disc length and 175 mm disc width; distal coloration of tail posterior to caudal stings usually dark purplish-brown; and features of the ventral lateral-line canals (hyomandibular canal very narrow, infraorbital and supraorbital canals not undulated, supraorbital and infraorbital loops small and narrow, supraorbital loop very short, not extending posteriorly to level of mouth, jugular and posterior infraorbital canals short, not extending caudally to first gill slits, subpleural loop very narrow posteriorly; absence of anterior and posterior subpleural tubules). To provide a foundation for the description of P. nana sp. nov., morphological variation in P. iwamae was examined based on all type specimens as well as newly collected and previously unreported material. Two specimens topotypic with the male paratype of P. nana sp. nov., referred to here as Plesiotrygon cf. iwamae, are also reported. Relationships of the new species to P. iwamae are discussed; further characters indicative of Plesiotrygon monophyly are proposed, but the genus may still not be valid. Plesiotrygon nana sp. nov., is commercialized with some regularity in the international aquarium trade from Iquitos (Peru), an alarming circumstance because nothing is known of its biology or conservation requirements.

Sand fly captures with Disney traps in area of occurrence of Leishmania (Leishmania) amazonensis in the state of Mato Grosso do Sul, mid-western Brazil

INTRODUCTION: The work was conducted to study phlebotomine fauna (Diptera: Psychodidae) and aspects of American cutaneous leishmaniasis transmission in a forested area where Leishmania (Leishmania) amazonensis occurs, situated in the municipality of Bela Vista, State of Mato Grosso do Sul, Brazil. METHODS: The captures were conducted with modified Disney traps, using hamster (Mesocricetus auratus) as bait, from May 2004 to January 2006. RESULTS: Ten species of phlebotomine sandflies were captured: Brumptomyia avellari, Brumptomyia brumpti, Bichromomyia flaviscutellata, Evandromyia bourrouli, Evandromyia lenti, Lutzomyia longipalpis, Psathyromyia campograndensis, Psathyromyia punctigeniculata, Psathyromyia shannoni and Sciopemyia sordellii. The two predominant species were Ev bourrouli (57.3%) and Bi flaviscutellata (41.4%), present at all sampling sites. Two of the 36 hamsters used as bait presented natural infection with Leishmania. The parasite was identified as Leishmania (Leishmania) amazonensis. CONCLUSIONS: Analysis of the results revealed the efficiency of Disney traps for capturing Bichromomyia flaviscutellata and the simultaneous presence of both vector and the Leishmania species transmitted by the same can be considered a predictive factor of the occurrence of leishmaniasis outbreaks for the human population that occupies the location.

Collision probabilities in the rarefaction fan of asymmetric exclusion processes

We consider the one-dimensional asymmetric simple exclusion process (ASEP) in which particles jump to the right at rate p is an element of (1/2, 1.] and to the left at rate 1 - p, interacting by exclusion. In the initial state there is a finite region such that to the left of this region all sites are occupied and to the right of it all sites are empty. Under this initial state, the hydrodynamical limit of the process converges to the rarefaction fan of the associated Burgers equation. In particular suppose that the initial state has first-class particles to the left of the origin, second-class particles at sites 0 and I, and holes to the right of site I. We show that the probability that the two second-class particles eventually collide is (1 + p)/(3p), where a collision occurs when one of the particles attempts to jump over the other. This also corresponds to the probability that two ASEP processes. started from appropriate initial states and coupled using the so-called ""basic coupling,"" eventually reach the same state. We give various other results about the behaviour of second-class particles in the ASEP. In the totally asymmetric case (p = 1) we explain a further representation in terms of a multi-type particle system, and also use the collision result to derive the probability of coexistence of both clusters in a two-type version of the corner growth model.

Changes in cigarette smoking among adults in 35 populations in the mid-1980s

Objective-To examine changes in the prevalence of cigarette smoking in 35 study populations of the World Health Organisation's MONICA Project. Design-Data from two independent, community-based surveys conducted, on average, five years apart. Setting-Geographically defined populations in 21 countries mainly in eastern and western Europe. Subjects-Randomly selected men and women aged 25-64 years. Numbers of participants in each study population ranged from 586 to 2817 in each survey. Main outcome measures-Changes in proportions of current smokers, ex-smokers, and never-smokers by age and sex using data collected by standardised methods. Results-Among men, smoking prevalence decreased in most populations, by three to four percentage points over five years. In Beijing, however, it increased in all age groups-overall by 11 percentage points. Among women there were increases in smoking in about half the populations. The increases were mainly in the age group 35-54 years and often in those populations where smoking prevalence among women has been relatively low. Conclusions-Smoking initiation by middle-aged women in parts of southern and eastern Europe and among men of all ages in Beijing is a matter of concern. The various public health measures that have helped to reduce smoking among men in developed countries should be vigorously extended to these other groups now at growing risk of smoking-related disease.