Hypothesis for a submarine landslide and cohesionless sediment flows resulting from a 17th century earthquake-triggered landslide in Quebec,Canada

Textural isotopic and microfossil data from two gravity cores obtained in Saguenay Fjord, Quebec, suggest that a distinctive sandy clay bed was deposited as the result of a major landslide in the Saguenay River basin. Pb-210 dating of the cores indicate that the bed is of similar age to the magnitude 7 earthquake of February 5, 1663. The slide involved sensitive marine clays and may have occurred in two stages. Slide sediments carried into the Saguenay River channel were probably reworked and subsequently transported down the Fjord basin as two distinct cohesionless mass flows. Fine clay laminae that overlie the older mass flow bed record the modulation of depositional processes by tidal currents for several weeks after this event.     

A multidisciplinary approach to evaluating impacts of shellfish aquaculture on benthic communities

The impact of suspended mussel culture (Mytilus edulis, M. trossulus) on the benthos of a small Nova Scotia cove (7 m depth) was assessed using meehods involving both benthic metabolism and community structure. Due to deposition of mussel feces and pseudofeces, sedimentation rate was higher under the mussel culture lines than at an adjacent reference site of similar sediment texture. Porewater profiles of sediment sulfate and sulfide indicated greater anaerobic metabolism at the mussel site than at the reference site, but sulfide was absent from the upper centimeters of sediments under the mussels. Seasonal measures of sediment oxygen demand showed little change between sites, but maximum rates of ammonium release at the mussel site were twice the highest rates measured at the reference site. Abundance of benthic macrofauna was higher at the reference site, but biomass was generally lower. Biomass at the mussel site was dominated by molluscs (Ilyanassa spp. andNucula tenuisulcata), that were attracted to mussels fallen from the culture and/or enriched organic matter due to biodeposition. Species diversity was lower at the reference site due to the dominance of the polychaeteNephtys neotena. Abundance-biomass comparisons (ABC method) of faunal analysis did not indicate any impact of biodeposition at this site: however, disturbance did not result in a typical assemblage of small opportunistic species anticipated with this method. Cluster analysis of macrofauna usually provided a clear separation between the sites. Since the contruction of a causeway (1968), foraminifera species composition showed a temporal response to temperature changes in the cove by shifting toward calcareous species, but assemblages downcore showed little or no relationship to aquaculture impacts. Although there is a shift toward anaerobic metabolism at the mussel lines, the impact of mussels falling to the sediments was more noticeable in benthic community structure than was any impact due to organic sedimentation or hypoxia. In general the impact of aquaculture on the benthos appeared to be minor. Furtyher assesment of these consequences may mandate both taxonomic and energetic approaches to impact assessment.     

西准噶尔包古图地区地层火山岩锆石LA-ICP-MS U-Pb年代学研究

包古图地区位于西准噶尔东南部,区内出露地层主要为石炭系太勒古拉组、包古图组和希贝库拉斯组,为一套巨厚的半深海相-大陆坡相火山-火山碎屑沉积建造。这套地层的时代归属和地层层序长期以来一直存在争议。本文报导了包古图地区实测地层剖面,并从太勒古拉组玄武岩和包古图组及希贝库拉斯组凝灰岩中分别选出锆石,进行了LA-ICP-MS U-Pb年代学研究,获得²⁰⁶Pb/²³⁸U加权平均年龄分别为357.5±5.4Ma、332.1±3.0Ma和336.3±2.5Ma。由此确定这套地层属于早石炭世的杜内阶到维宪阶,由下到上依次为太勒古拉组、包古图组和希贝库拉斯组。     

Artisanal fishing areas and traditional ecological knowledge: The case study of the artisanal fisheries of the Patos Lagoon estuary (Brazil)

One hundred and twenty-four fishing areas were identified and georeferenced according to fishermen's traditional ecological knowledge. Nearly 80% of the designations of the fishing areas were known by fishermen only and are registered for the first time. Fishermen identify fishing areas according to depth, wooden logs used to anchor fixed nets, gradation of water transparency, and traditional use of certain areas. This study reveals the richness of knowledge held by fishermen, it illustrates their solid straight relationship with the natural environment where they live, and shows the potential uses of TEK for fisheries management.     

Photogrammetric application of viking orbital photography

Special techniques are described for the photogrammetric compilation of topographic maps and profiles from stereoscopic photographs taken by the two Viking Orbiter spacecraft. These techniques were developed because the extremely narrow field of view of the Viking cameras precludes compilation by conventional photogrammetric methods. The techniques adjust for internal consistency the Supplementary Experiment Data Record (SEDR—the record of spacecraft orientation when photographs were taken) and the computation of geometric orientation parameters of the stereo models. A series of contour maps of Mars is being compiled by these new methods using a wide variety of Viking Orbiter photographs, to provide the planetary research community with topographic information.     

用活有孔虫分布指示三亚汊道外港潮流格局

由因子分析得知,海南岛三亚湾汊道外港海底分布有四个主因子活有孔虫群,它们分别代表海湾内水体、湖冲出半盐水水体、湾外内陆架水体及内陆架与海湾水相混的过渡水体.这些水体在潮汐作用下的运动、相互混合,可由各水体的有孔虫指示.由每个主因子因子得分最高的三个属种百分含量之和等值线图所指示的外港潮流循环格局,与海洋学研究所得的结果相当一致.利用有孔虫指示潮汐汊道潮流格局尚属首次尝试,这方法对海岸开发分析泥沙运动、污染物排放等有实践意义.     

Accurate parameter estimation for star formation history in galaxies using SDSS spectra

To further our knowledge of the complex physical process of galaxy formation, it is essential that we characterize the formation and evolution of large data bases of galaxies. The spectral synthesis starlight code of Cid Fernandes et al. was designed for this purpose. Results of starlight are highly dependent on the choice of input basis of simple stellar population (SSP) spectra. Speed of the code, which uses random walks through the parameter space, scales as the square of the number of the basis spectra, making it computationally necessary to choose a small number of SSPs that are coarsely sampled in age and metallicity. In this paper, we develop methods based on a diffusion map that, for the first time, choose appropriate bases of prototype SSP spectra from a large set of SSP spectra designed to approximate the continuous grid of age and metallicity of SSPs of which galaxies are truly composed. We show that our techniques achieve better accuracy of physical parameter estimation for simulated galaxies. Specifically, we show that our methods significantly decrease the age–metallicity degeneracy that is common in galaxy population synthesis methods. We analyse a sample of 3046 galaxies in Sloan Digital Sky Survey Data Release 6 and compare the parameter estimates obtained from different basis choices.     

Metals in marine sediments near a large California municipal outfall

Elevated concentrations of trace metals in surficial sediments off Palos Verdes Peninsula, site of the Los Angeles County outfall system, clearly reflect the submarine discharge of treated municipal (domestic and industrial) wastewater. The following contamination factors (median outfall/median baseline) were obtained for the eight metals measured in a 45 km² region of the outfall monitoring zone: Ag-27; Cd-36; Cr-12; Cu-20; Hg-23; Ni-5.4; Pb-17; Zn-7.7.