Strike-slip tectonic processes in the northern Caribbean between Cuba and Hispaniola (Windward Passage)

Marine geophysical data including Seabeam, seismic reflection, magnetics, gravimetry and side-scan sonar have been recently collected along the northern Caribbean strike-slip plate boundary between Cuba and Hispaniola, in the Windward Passage area. The analysis of this comprehensive data set allows us to illustrate active strike-slip tectonic processes in relation to the kinematics of the Caribbean Plate. We show that the transcurrent plate boundary trace runs straight across the Windward Passage, from the southern Cuban Margin in the west (Oriente Fault) to the Tortue Channel in the east. The Windward Passage Deep is thus not an active pull-apart basin, as previously suggested. The plate boundary geometry implies that the motion of the Caribbean Plate relative to the North American Plate is partitioned between a strike-slip component, accommodated by the Windward Passage active fault zone, and a convergence component, accommodated by compression at the bottom of the Northern Hispaniola Margin. On the basis of a correlation with onland geological data, an age is given to the stratigraphic sequences identified on seismic profiles. A kinematic reconstruction is proposed that follows the tectonic unconformities recognized at sea and on land (Late Eocene, Early Miocene, Middle Miocene and Late Pliocene). Each one of these tectonic events corresponds to a drastic reorganization of the plate boundary geometry. We propose to correlate these events with successive collisions of the northern Caribbean mobile terranes against the Bahamas Bank. During each event, the plate boundary trace is shifted to the south and a part of the Caribbean Plate is accreted to North America.     

Abrupt axial variations along the slow to ultra-slow spreading centers of the northern North Fiji Basin (SW Pacific): Evidence for short wave heterogeneities in a back-arc mantle

This study presents results of surveys conducted along the slow to ultra-slow spreading axis of the Northern North Fiji Basin (NNFB), including the Hazel Holmes, Tripartite and South Pandora Ridges, and the newly discovered Futuna and North Cikobia spreading centers. Spreading segments along these axes display highly contrasted axial morphologies, ranging from a rift valley to a prominent axial high. In some places, abrupt inversions of topography are observed between neighboring segments. Detailed analyses of bathymetry and backscatter maps reveal that axial highs are spotted with numerous coalescent volcanoes forming features ranging from irregular terrains to well-organized ridges. The volcanic edifices are distributed over a wide neovolcanic zone, which corresponds to the axial relief, suggesting on important contribution of volcanism to the relief construction. Comparisons between various ridge-shaped segments reveal that axial volcano-tectonic patterns are directly related to the local magma production and delivery, in a context of tectonic extension related to plate divergence, and suggest that coalescent volcanoes are fed from multiples short-lived and unconnected magma lenses. In the competition between horizontal and vertical accretion of oceanic crust, the spreading centers of the NNFB represent a special case where lava production is locally high enough and spreading rate is low enough to allow prominent axial highs to develop. The along axis morphologic variability is related to intermittent volcanic activity that may result from rapid temporal and spatial variations in the distribution of upper mantle convection cells below accretion centers, superimposed on the regional thermal anomaly located under the whole basin.     

Agonistic effect of imidazole and triazole fungicides on in vitro oocyte maturation in rainbow trout (Oncorhynchus mykiss)

The purpose of the present study was to assess the in vitro effect of some imidazole (prochloraz, imazalil) and triazole (epoxiconazole) agricultural fungicides on gonadotropin-induced oocyte maturation in rainbow trout. Results show that prochloraz, epoxiconazole and imazalil strongly potentiated the induction of oocyte maturation by gonadotropin in a dose-dependent manner. Furthermore, 10⁻⁵ M prochloraz and epoxiconazole alone induced oocyte maturation. The mRNA biosynthesis inhibitor, actinomycin , completely inhibited oocyte maturation induced by fungicides, suggesting that the gonadotropin-like effect of these chemicals is at least dependent on de novo gene expression.     

A comparative study of contaminant levels in Long Island Sound

This paper uses results from the National Oceanic and Atmospheric Administration’s National Status and Trends Program (NS&T) to place the environmental quality of Long Island Sound in a broader perspective. It compares levels of contaminants in blue mussels from ten Long Island Sound sites and in sediments from seven Long Island Sound sites with concentrations in the same media at 87 and 221 other sites, respectively, where comparable samples were obtained. In sediments, the levels of both trace metals and organic contaminants tend to be relatively high for Long Island Sound sites. This is especially true for five of the twelve metals (silver, cadmium, copper, lead, and zinc) and for five of six categories of organic contaminants (total chlordane, low molecular weight polycyclic aromatic hydrocarbons (PAHs), high molecular weight PAHs, total polychlorinated biphenyls, and total dichlorodiphenyltrichloroethanes). In mussels, the organic contaminant categories exhibit relatively high levels, but this is not true for most of the metals. In fact, four of the metals—arsenic, mercury, selenium, and zinc—show evidence of relatively low levels in mussels from Long Island Sound compared to other NS&T locations.     

Electron groups traced from the sun to 1 AU

We trace electrons from the Sun by a variety of proxy methods - solar flare positions, and metric and kilometric type III radio bursts from the Sun until they can be observed in situ as electrons at the ISEE-3 spacecraft. Our study extends over the period of operation of the electron experiment on ISEE-3 from August 1978 to November 1979. By carefully restricting timing within the data sets involved, we find a peak in the number of flares associated with in situ electrons near 60° west solar longitude. This peak shows that type III bursts can be fairly limited in spatial extent, and that the best connection with the solar surface to the flare is along the Archimedean magnetic field spiral. We use this spatial determination to define an average beam shape for an event. We assume this average beam shape to be representative of the distribution in space of each electron group. The electron numbers at 2 and 29–45 keV energies combined with this average beam shape are used to approximate the total numbers of electrons and energy per burst for individual events. We find that the total number of electrons and total energy for events varies significantly with flare type; that on the average brighter flares are associated with more electrons.     

Carrying capacity of the eastern ecological gradient of Kenya

Kenya's rate of natural population increase exceeds 4.0%/year. At this rate, Kenya's population of 23.5 million will expand to 35 million by the year 2000. Rural migrants are being forced out of the highlands into marginal arid and semiarid regions to the east and south in the eastern ecological gradient including Meru, Kitui, Machakos, and Kajiado districts. The people have become victims of marginalization by which the productivity of a unit of land declines relative to the demands of its occupants. The concept of carrying capacity means the number of people a given area can sustain over the long term. In Maasailand, 3.5 standard stock units (450 kg each) are required per adult equivalent for full subsistence, about 7 cows/person. For the Maasai pastoralists, carrying capacities were examined at 2 levels of subsistence: 100% from the herds and 80% from the herds; 2 technological levels; and population-growth rates of 2%, 2.5%, and 3%/annum. Using the median, 3.5%/year, population-growth scenario these districts will have almost 5 million inhabitants in the year 2000. Poverty at technology level I for 40% of them, or for 2 million people, is implausible. Technology level II implies that current rural-development programs will succeed with technological innovations for farm households, access to credit, and markets for their produce. Level II is likely to prevail toward the end of the century for the majority of farmers. Level III necessitates best agricultural and livestock technology as well as the best management. At most, 25% of the households of the eastern ecological gradient could enter this realm by the year 2000. Current strategies of voluntary family planning, rural development emerging from an antiquated extension system, inability to address inequity in land distribution, and laissez-faire resource management are inadequate to deal with the pace of change.     

Woolly rhino discovery in the lower Kolyma River

A nearly complete frozen mummy of a woolly rhinoceros (Coelodonta antiquitatis Blum., 1799) was discovered in a gold mine on the lower reaches of the Kolyma River, north–eastern Siberia. This is the first find of the whole body of woolly rhino in permafrost. A large part of the mummified body was preserved, including the left part of the body, covered by skin, including skin of the head and ear, fore and hind legs. The skull with 2 horns and the lower jaw were also preserved. Most of the internal organs were lost, except the intestines, stomach, and their contents. A rib fragment from this individual was dated by AMS-radiocarbon method to 39,140 ± 390 years BP (OxA-18755). Spore and pollen analyses of the stomach contents indicate that grasses and sagebrushes formed the main part of the diet of C. antiquitatis in this region of Arctic Siberia.     

Third-order depositional sequences reflecting Milankovitch cyclicity

The origin of third-order depositional sequences remains debatable, and in many cases it is not clear whether they were controlled by tectonic activity and/or by eustatic sea-level changes. In Oxfordian and Berriasian–Valanginian carbonate-dominated sections of Switzerland, France, Germany and Spain, high-resolution sequence-stratigraphic and cyclostratigraphic analyses show that the sedimentary record reflects Milankovitch cyclicity. Orbitally induced insolation changes translated into sea-level fluctuations, which in turn controlled accommodation changes. Beds and bedsets formed in rhythm with the precession and 100-kyr eccentricity cycles, whereas the 400-kyr eccentricity cycle contributed to the creation of major depositional sequences. Biostratigraphical data allow the correlation of many of the 400-kyr sequence boundaries with third-order sequence boundaries recognized in European basins. This implies that climatically controlled sea-level changes contributed to the formation of third-order sequences. Furthermore, this cyclostratigraphical approach improves the relative dating of stratigraphic intervals.