Glaciovolcanic landsystems and large-scale glaciotectonic deformation along the Brekknafjöll–Jarlhettur,Iceland

This paper documents the glaciovolcanic landsystem of the Brekknafjöll–Jarlhettur ridge in Central Iceland. Glaciolacustrine diamict is found beneath, and in association with, a complex assemblage of pillow lava, lava breccias and hyaloclastites. Three depositional environments are identified: glaciolacustrine fan, pillow lava dome, and hyaloclastite fan. These subaqueous environments occurred both simultaneously and at different times along the volcanic fissures which underlie the ridge and have given rise to a complex facies architecture. This facies architecture provides evidence that the ridge evolved in a time transgressive fashion during several episodes of volcanism, some of which may have been punctuated by periods of ice erosion. Associated with the ridge are large-diapiric folds in diamict and gravel which form by the loading and lateral displacement of saturated diamict beneath the developing volcanic pile. A depositional model is presented which emphasises the glaciolacustrine component and the time transgressive nature of the glaciovolcanic landsystem. Much of the eruption occurred in subglacial to englacial lakes or vaults, which were probably linked by water and sediment exchange. The initial subglacial vaults appear to have extended beyond the fissure limits and were infilled by glaciolacustrine diamicts, subaqueous outwash and the eruption of pillow lava. This was followed by the eruption of hyaloclastite sand and breccia forming an elongated fan.     

The density of North Atlantic and North Pacific deep waters

The densities of seventeen samples of seawater from GEOSECS stations 27 (North Atlantic) and 217 (North Pacific) have been measured with a vibrating flow densimeter at 25°C. The densities of the deep samples were found to be 5 ± 1.5and16 ± 3.6ppm greater, for the North Atlantic and North Pacific, respectively, than predicted by the equation of state of Millero, Gonzalez and Ward (1976) derived for seawaters of constant relative composition. The results are in good agreement with the density anomalies predicted by Brewer and Bradshaw (1975) on the basis of the observed increase of dissolved silica, alkalinity and total carbon dioxide in oceanic deep waters. The application of these corrections results in an agreement with the Millero, Gonzalez and Ward (1976) equation of state to ±4 ppm.     

Temporal and spatial persistence in rainfall records from Northeast Brazil and Galicia (Spain)

Summary Temporal and spatial persistence effects in historical rainfall records are investigated for a large number of stations from Northwest Spain (Galicia) and Northeast Brazil. Quantitative results, expressed by the Hurst or roughness exponent, are obtained by two methods: the R/S analysis and the semi-variogram. Despite rather different climatic conditions and period of analysis for the two regions, the results indicate that persistence and anti-persistence for the temporal and spatial analyses, respectively, are found for both regions. Temporal persistence is known to occur with other climatic fields and in many different regions of the world. Antipersistence in spatial patterns of rainfall is a strong result of this work, despite its apparent contradiction with temporal persistence. The results for Northeast Brazil support previous indications of a geographic stratification of persistence: both temporal and spatial persistence increase as latitude decreases.     

Magnetic storms

This talk provides a brief summary of the first conference devoted entirely to magnetic storms. The conference was held in Pasadena, California, at the Jet Propulsion Laboratory, 12-16 February 1996. Topics covered the relevant time-varying phenomena at the sun/corona, propagation of these structures through interplanetary space, the response of the magnetosphere from its interaction with these interplanetary structures, the formation of the storm- time ring-current (in particular the oxygen content of the ring-current), and storm ionospheric effects and ground based effects. A complementary summary is provided by Gonzalez et al. in EOS, 1996. The full set of review articles will be published in an AGU monograph and many of the contributed articles will appear in a special section of the Journal of Geophysical Research, Space Physics.     

Biogeochemical aromatic markers in the sediments from mahakam delta (Indonesia)

Analysis of the tri-, tetraand pentaaromatic hydrocarbon fractions of several sediments (0–600 m) from the Mahakam Delta (Indonesia), indicate the predominance of polycyclic aromatic hydrocarbons (PAH) diagenetically related to triterpenoid natural precursors. High resolution Shpol'skii spectrofluorometry (HRS) proved to be a valuable analytical tool, in conjunction with high performance liquid chromatography (HPLC) and capillary gas chromatography coupled with mass spectrometry (CGC/MS), for the identification of individual components in Chromatographic fractions obtained after a high resolution reverse phase liquid chromatography.     

Organic geochemistry of Recent equatorial deltaic sediments

The organic matter of recent deltaic sediments cored in the Mahakam delta, East Kalimantan, has been studied before and after physical fractionation into sands >50 μm, silts 5–50 μm and clays <5 μm. Both the lipid and non-lipid components have been investigated.Weight, carbon and nitrogen fractionation budgets were used to define three types of samples, depending on coarse particle contributions to the total amount of organic matter: a = a first type with more than 50% of the O.M. in the coarse particles, high C/N ratios and O.M. content, b = an intermediary type with medium C/N ratios and O.M. content, each fraction having quite the same O.M. content, c = a third type with less than 5% of the whole O.M. in the sands and the lowest C/N ratios and O.M. content.Concerning the global organic characteristics of the fractions, a systematic increase of C/N ratios occurs when going from clays to sands; the finer the fraction is, the more nitrogenous the compounds are. This enrichment in nitrogen is related to a persistent high rate of hydrolysable material either for argillaceous organic matter-poor sediments or for the clay fractions of all types of samples. Conversely, the type (a) coarse sediments, in particular the sandy components were resistant to acid hydrolysis with burial.Concerning the geochemical markers signatures of granulometric fractions, the distribution patterns of n-alkanes and n-fatty acids are characterized by the predominance of high molecular weight compounds >C₂₂. Carbon preference index (CPI) values are higher in the sands and silts, reflecting their enrichment in continentally-derived vegetation debris. For type (c), the fractionation revealed markers of microbial activity within the clay fractions. For all types of samples, we observed an increase with burial of the n-alkane and n-fatty acid concentrations, particularly in the clay fractions, suggesting possibly a better preservation and/or affinity of lipids with the finest fractions.     

“A Salute to the Bandido”: A Political Ecology of Voice Exploration into Peru’s Freedom of Voice Surrounding Hydrocarbon Development

This paper sets out to evaluate the freedom of voice for Peruvian stakeholders affected by hydrocarbon development. This occurs through the utilization of a political ecology of voice (PEV) theoretical framework based upon the theory of voice by Albert Hirschman and political ecology. PEV can be defined as the study of economic, political, social, and geographical factors over a specific time period and their impact upon the use of voice by stakeholders. Peru’s case study was focused on its main oil-producing Loreto Region and incorporated evaluation of hydrocarbon voice mechanisms (prior consultation and environmental impact assessments) supported by interview testimony of stakeholders and state officials. PEV analysis reveals a political environment which is dangerous, inflexible, and intolerant of Peruvian stakeholders voicing over hydrocarbon development. This is due to the state’s zealous pursuit of its “selva (rainforest) hydrocarbon and development vision” which severely undermines Peruvian stakeholder’s freedom of voice.     

Influence of the South Atlantic convergence zone and SouthAtlantic Sea surface temperature on interannual summerrainfall variability in Southeastern South America

Summary  In subtropical Argentina, Paraguay and southern Brazil, precipitation is most abundant during summer but its interannual variability is large. At this time a zone of low-level convergence, upper-level divergence, and intense convection is developed to the north of this area. This feature is known as the South Atlantic convergence zone (SACZ) and seems to be related to the interannual variability of summer rainfall to its south. The aim of this work is to document this relationship. Reduced (increased) precipitation in southern Brazil, most of Uruguay and northeastern Argentina is associated with a strong (weak) SACZ and a northward (southward) displacement of it, while increased (reduced) rainfall occurs further south in subtropical Argentina. Also, warm (cold) SST in the region 20° S–40° S and west of 30° W is likely accompanied by a southward (northward) shift of the SACZ. Aside of this relation with the SACZ that affect on the precipitation field of Southeastern South America, the proximate Atlantic Ocean SST seems to force the precipitation over this region by other mechanisms as well. The result of this additional SST forcing is to enhance the signal of the SACZ in northeastern Argentina, Uruguay and southern Brazil and to oppose the SACZ effect in southern subtropical Argentina. Received July 24, 1999 Revised July 5, 2000     

The 2005 eruption of Ilamatepec (Santa Ana) volcano,El Salvador

We report the stratigraphic sequence of the 2005 eruption of Ilamatepec volcano together with sedimentological and chemical analyses of its products.Structural and textural characteristics of the deposits indicate that the eruption was driven by a small-volume rhyolitic intrusion at shallow levels, which resulted first in the collapse of the existing hydrothermally altered fan of previous deposits inside the crater lake, driving phreatic explosions with launching of blocks on ballistic trajectories; later the magma interacted with lake waters producing several hydromagmatic pyroclastic density currents (PDCs). These flows were energetic enough to knock down pine trees up to distances of 1.8 km from the crater in the E-NE sector of the volcano. Finally, ejection of ballistic blocks that landed on previously emplaced, wet pyroclastic density current deposits, caused the generation of a lahar that flowed down the steep eastern flank toward the El Jabillal gully. Subsequent lahars occurred as a result of intense rain caused by hurricane Stan.Radiocarbon ages on paleosols and charcoal fragments, separating previous volcanogenic sequences, indicate that similar eruptions have occurred more frequently in the past centuries, than previously thought.The new data confirms that Ilamatepec volcano is one of the most active volcanoes in El Salvador. Nevertheless, more detailed studies of the eruptive sequence of Ilamatepec volcano are mandatory to establish future eruptive patterns.     

运用生物地理学理论与遥感影像寻找本·拉登

本·拉登到底在哪里？这是我们这个时代最重要的政治问题之一。在这篇文章中,我们依据反映生物分布和灭绝规律的生物地理学理论(距离衰减理论、岛屿生物地理理论、本·拉登个人数据),结合遥感数据(陆地卫星 ETM+、航天雷达地形测图、QuickBird),从全球、区域、局部三个空间尺度分析并最终指出本·拉登当前最可能的所在地。这是第一次运用科学手段来确定本·拉登居所。该方法具有可重复性：一旦美国情报部门提供新的信息,便可通过该方法重新定位本·拉登当前最有可能的藏身场所。