Mantle flow, volatiles, slab-surface temperatures and melting dynamics in the north Tonga arc-Lau back-arc basin

The Fonualei Spreading Center affords an excellent opportunity to evaluate geochemical changes with increasing depth to the slab in the Lau back-arc basin. We present H2O and CO2 concentrations and Sr, Nd, Pb, Hf and U-Th-Ra isotope data for selected glasses as well as new Hf isotope data from boninites and seamounts to the north of the Tonga arc. The Pb and Hf isotope data are used to show that mantle flow is oriented to the southwest and that the tear in the northern end of the slab may not extend east as far as the boninite locality. Along the Fonualei Spreading Center, key geochemical parameters change smoothly with increasing distance from the arc front and increasing slab surface temperatures. The latter may range from 720 to 866 degrees C, based on decreasing H2O/Ce ratios. Consistent with experimental data, the geochemical trends are interpreted to reflect changes in the amount and composition of wet pelite melts or super-critical fluids and aqueous fluids derived from the slab. With one exception, all of the lavas preserve both U-238 excesses and Ra-226 excesses. We suggest that lavas from the Fonualei Spreading Center and Valu Fa Ridge are dominated by fluid-fluxed melting whereas those from the East and Central Lau Spreading Centers, where slab surface temperatures exceed similar to 850-900 degrees C, are largely derived through decompression. A similar observation is found for the Manus and East Scotia back-arc basins and may reflect the expiry of a key phase such as lawsonite in the subducted basaltic crust.

The Kepler-10 Planetary System Revisited by HARPS-N: A Hot Rocky World and a Solid Neptune-Mass Planet

Kepler-10b was the first rocky planet detected by the Kepler satellite and confirmed with radial velocity follow-up observations from Keck-HIRES. The mass of the planet was measured with a precision of around 30%, which was
insufficient to constrain models of its internal structure and composition in detail. In addition to Kepler-10b, a second planet transiting the same star with a period of 45 days was statistically validated, but the radial velocities were only
good enough to set an upper limit of 20 M⊕ for the mass of Kepler-10c. To improve the precision on the mass for planet b, the HARPS-N Collaboration decided to observe Kepler-10 intensively with the HARPS-N spectrograph
on the Telescopio Nazionale Galileo on La Palma. In total, 148 high-quality radial-velocity measurements were obtained over two observing seasons. These new data allow us to improve the precision of the mass determination for Kepler-10b to 15%. With a mass of 3.33 ± 0.49 M⊕ and an updated radius of 1.47+0.03 −0.02 R⊕, Kepler-10b has a density of 5.8 ± 0.8 g cm−3, very close to the value predicted by models with the same internal structure and composition as the Earth. We were also able to determine a mass for the 45-day period planet Kepler-10c, with an even better precision of 11%. With a mass of 17.2 ± 1.9 M⊕ and radius of 2.35+0.09 −0.04 R⊕, Kepler-10c has a density of 7.1 ± 1.0 g cm−3. Kepler-10c appears to be the first strong evidence of a class of more massive solid planets with longer orbital periods

Stable Isotope Dietary Analysis of Prehistoric Populations from the Minusinsk Basin, Southern Siberia, Russia: A new chronological framework for the introduction of millet to the eastern Eurasian steppe

We report the results of stable carbon and nitrogen isotope analysis of 354 human and faunal samples from five archaeological cultures of the Minusinsk Basin, Southern Siberia – Afanasyevo, Okunevo, Andronovo, Karasuk and Tagar (ca. 2700–1 BC) – a key location in Eurasia due to its position on a northern corridor linking China and central Eurasia. The results indicate that the diet of Eneolithic to Middle Bronze Age (Afanasyevo to Andronovo) populations was primarily C3-based, with C4 plants only becoming an important component of the diet in the Late Bronze Age Karasuk and Early Iron Age Tagar cultures. Freshwater fish seems to have been an important constituent of the diets in all groups. The findings constitute the earliest concrete evidence for the substantial use of millet in the eastern Eurasian steppe. We propose that it was probably introduced from Northwestern China during the Karasuk culture at the start of the Late Bronze Age, ca. 1500 BC. We conclude with a discussion of the implications for the nature of pastoralist economies on the steppes.

Diagenetic Alterations and Reservoir Quality Evolution of Lower Cretaceous Fluvial Sandstones: Nubian Formation, Sirt Basin, North-Central Libya

Lower Cretaceous meandering and braided fluvial sandstones of the Nubian Formation form some of the most important subsurface reservoir rocks in the Sirt Basin, north-central Libya. Mineralogical, petrographical and geochemical analyses of sandstone samples from well BB6-59, Sarir oilfield, indicate that the meandering fluvial sandstones are fine- to very fine-grained subarkosic arenites (av. Q91F5L4), and that braided fluvial sandstones are medium- to very coarse-grained quartz arenites (av. Q96F3L1). The reservoir qualities of these sandstones were modified during both eodiagenesis (ca. <70oC; <2 km) and mesodiagenesis (ca. >70oC; >2km). Reservoir quality evolution was controlled primarily by the dissolution and kaolinitization of feldspars, micas and mud intraclasts during eodiagenesis, and by the amount and thicknessof grain-coating clays, chemical compaction and quartz overgrowths during mesodiagenesis. However, dissolution and kaolinitization of feldspars, micas and mud intraclasts resulted in the creation of intercrystalline micro- and mouldic macro-porosity and permeability during eodiagenesis, which were more widespread in braided fluvial than in meandering fluvial sandstones. This was because of the greater depositional porosity and permeability in the braided fluvial sandstones which enhanced percolation of meteoric waters. The development of only limited quartz overgrowths in the braided fluvial sandstones, in which quartz grains are coated by thick illite layers, retained high porosity and permeability (12-23 % and 30- 600 mD). By contrast, meandering fluvial sandstones underwent porosity loss as a result of quartz overgrowth development on quartz grains which lack or have thin and incomplete grain-coating illite (2-15 % and 0-0.1mD). Further loss of porosity in the meandering fluvial sandstones occurred as a result of chemical compaction (pressuredissolution) induced by the occurrence of micas along grains contacts. Otherdiagenetic alterations, such as the growth of pyrite, siderite, dolomite/ankerite and albitization, had little impact on reservoir quality. The albitization of feldspars may have had minor positive influence on reservoir quality throughthe creation of intercrystalline micro-porosity between albite crystals.The results of this study show that diagenetic modifications of the braided and meandering fluvial sandstones in the Nubian Formation, and resulting changes in reservoir quality, are closely linked to depositional porosity and permeability. They are also linked to the thickness of grain-coating infiltrated clays, and to variations in detrital composition, particularly the amounts of mud intraclasts, feldspars and mica grains as well as climatic conditions.

Biogeochemical relationships of arsenic in the Haor Basin of Bangladesh

Biogeochemical relationships and the level of arsenic (As) contamination of groundwater and surface sediments in the Haor Basin of Bangladesh were assessed to see if surface sediments gave any indication of underlying As cycling. The Haor areas under study have been found to be affected with high As (up to 331 μg/L) in groundwater, with contamination of both shallow and deep aquifers. Highly significant relationships of As with Dissolved Organic Carbon (DOC) in groundwater and Total Carbon (TC) and Organic Carbon (OC) in sediments are indicative of reductive dissolution of iron (Fe) and/or manganese (Mn) oxides/oxyhydroxides coupled with biodegradation of organic matter as the dominant processes to release As in groundwater. This study also reveals that As geochemistry in the surface sediments has limited influence on As geochemistry in the groundwater of the Haor Basins. © 2012 Taylor & Francis Group.

Two species of caridean shrimps (Decapoda:Hippolytidae and Nematocarcinidae) newly recorded from hydrothermally vents on the Manus Basin, Southwestern Pacific.

Two species of caridean shrimps are newly recorded from hydrothermal vents on the Manus Basin, southwestern Pacific, at depths of 1540-1577m. Lebbeus manus, new species, is related to L.curvirostris Zarenkov, 1976, L.elegans Komai, Hayashi & Kohtsuka, 2004, L.longipes (Kobjakova, 1936), L.vicinus vicinus (Rathbun, 1902) and L.vicinus motereyensis (Wicksten & Mendez, 1982) because of the lack of strap-like epipods on the second and third pereopods; but characters of the rostrum, carapace and abdomen immediately distinguish the new species from the these five taxa. Subadult and juvenile specimens of Nematocarcinus are referred to N.sp.aff.exilis, but their definite identification is postponed until additional specimens become available for study. There are a few minor differences between the present Manus specimens and European specimens representing N.exilis (Bate, 1888), suggesting that the Manus population may indeed represent a separate species.

Evaluation of the contamination level and proposal of remediation of soils in the basin of a processing plant of heavy metals, under a tropical climate, in Minas Gerais, Brazil

Indústrias metalúrgicas de produção de ligas metálicas podem por em risco toda a área envolvente, nomeadamente a qualidade das águas (superficiais e subterrâneas), dos solos e do ar, sempre que não existam infraestruturas e planos adequados de gestão destes resíduos. No caso em estudo, a unidade industrial situa-se na bacia do rio São Francisco, no estado brasileiro de Minas Gerais, e nos mais de quarenta anos de funcionamento tem produzido inúmeros problemas ambientais. Este estudo baseia-se nos primeiros resultados referentes aos solos da envolvente, tendo como objetivos a identificação dos principais contaminantes e a definição da área contaminada, de forma a avaliar a eficácia de projetos futuros de recuperação.

Vertebrate diversity in the Bussaco Mountain and surrounding areas

A biodiversidade é fundamental para o funcionamento dos ecossistemas e, além do seu valor intrínseco, fornece bens e serviços essenciais ao Homem. É consensual que as reservas naturais, por si só, não conseguirão preservar a biodiversidade de modo a que seja travada a perda de espécies que vem acontecendo a ritmos sem precedente. Assim, compreender os padrões de distribuição das espécies à escala regional ou sub-regional, ainda que em territórios não classificados, é crucial para o estabelecimento de políticas de gestão que visem a conservação da biodiversidade. O principal objectivo deste trabalho centrou-se na descrição e compreensão dos padrões de riqueza específica, distribuição e abundância de Vertebrados face aos diversos habitats que constituem a área de estudo. Constituíram, assim, objecto de estudo os anfíbios, aves, morcegos, micromamíferos e mamíferos de médio porte. A Serra do Bussaco e áreas envolventes encontram-se dominadas por vastas extensões de monocultura de Pinus pinaster e Eucalyptus globulus e por terrenos agrícolas. A Mata Nacional do Bussaco, bosque extremamente diverso, é outro importante elemento de paisagem. Pretendeu-se então analisar o efeito das práticas silvícolas actuais e da intensificação da agricultura sobre a biodiversidade, averiguando a importância de cada tipo de habitat para os Vertebrados em geral, e para algumas classes em particular. De entre os terrenos agrícolas, é bastante claro que a agricultura tradicional, com a sua típica complexidade e disponibilidade de água, constitui um habitat muito importante para a maioria dos Vertebrados, tendo também apresentado o maior valor conservacionista. No que respeita aos habitats florestais, o bosque misto apresentou consistentemente maior riqueza específica e diversidade, afirmando-se como o habitat preferido para a maioria das espécies e aquele com maior valor conservacionista. Do ponto de vista da conservação, as monoculturas, especialmente as da uma espécie exótica, revelaram-se habitats relativamente pobres. No entanto, estas conclusões referem-se às tendências gerais, sendo que taxa particulares respondem de forma diferente, atendendo aos seus requisitos específicos. A informação recolhida fornece bases essenciais para a construção de linhas de orientação que visem a integração das actividades humanas com a manutenção da biodiversidade e respectivos serviços, presumivelmente com aplicação a outras áreas geográficas.

Ecological assessment of the red deer population in the Lousã Mountain

Durante o último século, as populações de cervídeos têm aumentado substancialmente um pouco por toda a Europa. O veado Cervus elaphus não foi exceção, apresentando atualmente uma ampla distribuição geográfica. Após a quase extinção de todas as populações selvagens desta espécie em Portugal, o número de efetivos de veado e a área de distribuição da espécie têm aumentado significativamente nas últimas décadas. Esta proliferação deveu-se fundamentalmente aos processos de reintrodução implementados em algumas zonas do país, como foi o caso da Serra da Lousã. Dez anos após a reintrodução, a expansão geográfica e demográfica é já uma realidade e a espécie assume um papel relevante tanto do ponto de vista cinegético como turístico. Com o aumento das populações de ungulados, surge a necessidade de aumentar o conhecimento existente sobre estas espécies, particularmente ao nível das estimativas populacionais, do uso e seleção de habitat, do comportamento e da fisiologia das populações. Neste sentido, um dos objetivos foi comparar quatro métodos de contagem de excrementos em termos de estimativa populacional, aplicabilidade e eficiência. Face aos resultados obtidos, o método de transectos lineares com distance sampling revelou-se o mais eficiente, providenciando uma boa precisão num menor tempo. Relativamente ao uso e seleção do habitat, recorrendo a transectos de contagem de excrementos e a observações diretas, verificou-se que o veado seleciona positivamente habitats que lhe proporcionam simultaneamente alimento e refúgio, como é o caso das áreas de ecótono. A preferência por áreas de ecótono evidencia um comportamento adaptativo de maximização de energia, no qual os animais optam por procurar refúgio na proximidade das áreas de alimentação de forma a minimizarem os dispêndios energéticos. Em termos de dinâmica populacional, verificou-se uma relação entre a densidade de veado e o tamanho dos seus grupos, bem como o efeito nos mesmos do coberto vegetal. Contudo, dado o seu alto dimorfismo sexual em termos de tamanho corporal, as preferências de habitat podem também ser em parte responsáveis pela segregação sexual fora da época de reprodução. Face aos resultados obtidos através do método de observação direta de animais, a segregação sexual surge como consequência da interação entre fatores sociais e de habitat, que resultam de diferentes estratégias reprodutivas por parte de ambos os sexos. As diferentes estratégias reprodutivas são também notórias em termos de condição física e imunológica, com os machos a aumentarem a sua condição durante as épocas de primavera e verão de forma a melhorarem a sua performance durante o cio, e as fêmeas a viverem grande parte do ano no limiar da condição física devido ao seu investimento na sobrevivência da sua descendência. Globalmente, o veado apresenta uma boa adaptação à Serra da Lousã e representa um importante recurso natural para esta região. Contudo, para que a proliferação desta população selvagem continue, é necessária a implementação de medidas de gestão adequadas a este ecossistema mediterrâneo.

The effect of conservation measures on the spatial and temporal variation of rocky fish assemblages in the Arrábida Marine Park

Marine protected areas (MPAs) have been widely proposed for conservation purposes and as a tool for fisheries management. The Arrábida Marine Park is the first MPA in continental Portugal having a management plan, fully implemented since 2009. The main objective of this study was to evaluate the effect of protection measures on rocky reef fish assemblages and target invertebrates through before-after and control-effect (no-take vs. fished areas) underwater visual surveys and analysis of landings trends. Second, we used surveys before, during and after implementation of the management plan to understand fishers‟ preferences for fishing grounds and adaptation to the new rules, and evaluated the reserve effect through analysis of both ecological responses and fishing effort density. Third, we identified the main oceanographic drivers influencing the structure of reef fish assemblages and predicted the community structure for the last 50 years, in light of climatic change. Overall results suggest positive responses in biomass but not yet in numbers of some commercial species, with no effects on non-target species. The reserve effect is reinforced by the increase in landings of commercial species, despite increased fishing effort density in some areas, especially with octopus traps. Fishing grounds are mainly chosen based on the distribution of target species and associated habitats, but distance to port, weather conditions and safety also influence fishers‟ choices. Moreover, different fisheries respond differently to the protection measures, and within each fishery, individual fishers show distinct strategies, with some operating in a broader area whereas others keep preferred territories. Our results also show that wind stress and temperature are the main oceanographic drivers for rocky reef fish assemblages, with tropicalization of assemblages and polewards movements of species over the last 50 years consistent with temperature trends. We believe this study provides significant lessons for marine conservation and management of coastal systems.

Patterns of distribution in intertidal rocky shores: the role of grazing and competition in structuring communities

Tese de doutoramento, Ciências do Mar, Faculdade de Ciências do Mar e do Ambiente, Universidade do Algarve, 2000