Narrow Belt Research Articles

Emprego de krigagem ordinária para estimar a distribuição espacial de litofácies permeáveis: exemplo do Aquíferio Rio Claro em Paulínia/SP

A distribuição de valores de condutividade hidráulica representa uma informação crucial para elaboração de modelos matemáticos de fluxo e transporte de contaminantes, bem como para o planejamento e implantação de sistemas de remediação para remoção de contaminantes em subsuperfície. É prática comum a construção dos campos de condutividade hidráulica de informações discretas, obtidas a partir da construção de modelos geológicos. Contudo, tal abordagem apresenta como limitação a subjetividade na elaboração de tais modelos, uma vez que a adoção de critérios para definição da distribuição de fácies e contatos litológicos envolve algum grau de subjetividade. No presente trabalho é proposta uma abordagem distinta, em que informações geológicas de subsuperfície são convertidas em valores de condutividade hidráulica. Estes valores são empregados como dados de entrada para construção de campos tridimensionais de condutividade hidráulica, utilizando o método geoestatístico Krigagem ordinária. A distribuição dos valores de condutividade hidráulica acima de um ponto de corte indica a geometria e a conectividade das fácies permeáveis. Esta abordagem foi testada no Aquífero Rio Claro, em Paulínia (SP), a partir de dados geológicos de subsuperfície coletados em 255 pontos. Os resultados indicam que os valores elevados de condutividade hidráulica se distribuem ao longo de uma faixa contínua, de direção leste-oeste, e refletem o contexto deposicional do Aquífero Rio Claro na área. A geometria dos corpos arenosos tem importantes implicações para determinação da arquitetura de fácies da Formação Rio Claro no munícipio de Paulínia e, de maneira similar, no comportamento do fluxo de água subterrânea e transporte de contaminantes no aquífero raso local

Distribution patterns and controlling factors for reservoir characteristic difference of oolitic shoals, Feixian’guan Formation, eastern Longgang area, SW China

In eastern Longgang area of northeastern Sichuan Basin, the Kaijiang-Liangping trough was deposited with and leveled up by Feixian’guan sediments, where oolitic shoals exhibit progradation and upward migration. These oolitic shoals are classified into oolitic dolostone shoals and oolitic limestone shoals. The dolostone shoals occur within a narrow belt along Changxingian platform margin where the thickness of one single layer can be large; however, the cumulative thickness is rather small. On the contrary, the limestone shoals spread widely along shifted platform margin and is characterized by small thickness of one single layer and large cumulative thickness. Diagenesis has been found to play an important role in oolitic reservoir properties. The origin of low porosity and permeability in this extensive oolitic limestone reservoirs was attributed to burial cementation, while diagenetic processes, such as, reflux and hydrothermal dolomitization, have been identified as the primary factors for generating high-grade oolitic dolostones. Feixian’guan reservoir is characterized by low matrix porosity (which usually ranges from 2 to 3%). Existence of fractures may improve overall porosity and permeability of these reservoirs. The direct influence of these fractures may be to connect originally isolated pores to form a better connected pore-fracture system. Additionally, the fractures may have facilitated the migration of the organic acids that are associated with oil and gas, to help further enhance the quality of the reservoir through corrosion.

The scattered disc of HR 8799

HR~8799 is a young F0-type star with four directly imaged giant planets and two debris belts, one located exterior and another one interior to the region occupied by the planetary orbits. Having an architecture similar to that of our Solar System, but also revealing dissimilarities such as high masses of planets, a huge radial extent and a high mass of the outer debris belt, HR~8799 is considered to be a benchmark to test formation and evolution models of planetary systems. Here we focus on the outer debris ring and its relation to the planets. We demonstrate that the models of the outer disc, proposed previously to reproduce Herschel observations, are inconsistent with the ALMA data, and vice versa. In an attempt to find a physically motivated model that would agree with both observational sets, we perform collisional simulations. We show that a narrow planetesimal belt and a radiation pressure induced dust halo cannot account for the observed radial brightness profiles. A single, wide planetesimal disc does not reproduce the data either. Instead, we propose a two-population model, comprising a Kuiper-Belt-like structure of a low-eccentricity planetesimal population ("the classical Kuiper Belt") and a high-eccentricity population of comets ("scattered disc"). We argue that such a structure of the exo-Kuiper belt of HR~8799 could be explained with planet migration scenarios analogous to those proposed for the Kuiper Belt of the Solar System.

Transient photoreception in the hindbrain is permissive to the life history transition of hatching in Atlantic halibut

In nonmammalian vertebrates, photoreception takes place in the deep brain already early in development, but knowledge is lacking about the functions of these nonvisual photoreceptive systems. Prior to hatching, Atlantic halibut has a transient bilateral cluster of photoreceptive cells in the hindbrain. The cluster is imbedded in a neuronal network projecting to the narrow belt of hatching glands in the yolk sac. In halibut, hatching is inhibited in light and activated by transfer to darkness and c-fos analysis during hatching shows that the hindbrain cluster and hatching glands have neural activation. Unexpectedly, the hindbrain cluster expresses dual photopigments, vertebrate ancient opsin and melanopsin. Evolutionarily, these opsins are believed to belong to different classes of photopigments found in rhabdomeric and ciliary photoreceptors. The concept that an organism develops transient light sensitivity to target critical aspects of life history transitions as hatching provides a fascinating landscape to investigate the timing of other biological events.

Gypsum–anhydrites in 1.9 Ga Vempalle Formation, Cuddapah basin, India: A note on the Palaeoproterozoic environment and diagenetic condition

The Cuddapah basin consists of generally well-preserved Palaeoproterozoic–Neoproterozoic sedimentary and associated volcanic rocks. The detailed lithological studies of sedimentary rocks of Vempalle Formation from the narrow linear belt of 15 km, in the southern margin, show the occurrence of layered gypsum in the cherty dolostone–shale intercalated facies, red shale and phosphatic dolostone facies of the Vempalle Formation. The petromineralogical studies reveal that gypsum is in close association with anhydrites. Microscopically, three different types of gypsum and anhydrite are identified, viz., lath-shaped, equant-shaped and anhedral-shaped grains. The equant variety corresponds to a granular gypsum, whereas the anhedral grains of gypsum exist as the granular and fibrous variety as seen in the hand specimen. The presence of gypsum/anhydrite has been confirmed by the petromineralogical, X-ray diffraction and chemical analytical data. The phosphatic dolostone is the host rock for stratabound type of uranium deposit at Tummalapalle, Cuddapah district, Andhra Pradesh, which is one of the most unique types of uranium mineralisation in the world. Abundant pseudomorphs of gypsum and anhydrite relicts and discontinuous gypsum layers within these dolostones, nodules of chert and gypsum indicate the interrelationship between the diagenesis and genesis of uranium mineralisation which indicates the carbonate precipitation in the sulphate-rich hypersaline environments.

High-temperature metamorphism and crustal melting at ca. 3.2 Ga in the eastern Kaapvaal craton, southern Africa

The question of whether high-grade metamorphism and crustal melting in the early Archaean were associated with modern-style plate tectonics is a major issue in unravelling early Earth crustal evolution, and the eastern Kaapvaal craton has featured prominently in this debate. We discuss a major ca. 3.2 Ga tectono-magmatic-metamorphic event in the Ancient Gneiss Complex (AGC) of Swaziland, a multiply deformed medium- to high-grade terrane in the eastern Kaapvaal craton consisting of 3.66–3.20 Ga granitoid gneisses and infolded greenstone remnants, metasedimentary assemblages and mafic dykes. We report on a 3.2 Ga granulite-facies assemblage in a metagabbro of the AGC of central Swaziland and relate this to a major thermo-magmatic event that not only affected the AGC but also the neighbouring Barberton granitoid-greenstone terrane.Some previous models have related the 3.2 Ga event in the eastern Kaapvaal craton to subduction processes, but we see no evidence for long, narrow belts and metamorphic facies changes reflecting lithospheric suture zones, and there is no unidirectional asymmetry in the thermal structure across the entire region from Swaziland to the southern Barberton granite-greenstone terrane as is typical of Phanerozoic and Proterozoic belts. Instead, we consider an underplating event at ca. 3.2 Ga, giving rise to melting in the lower crust and mixing with mantle-derived under- and intraplated mafic magma to generate the voluminous granitoid assemblages now observed in the AGC and the southern Barberton terrane. This is compatible with large-scale crustal reworking during a major thermo-magmatic event and the apparent lack of a mafic lower crust in the Kaapvaal craton as shown by seismic data.

The iron limitation mosaic in the California Current System: Factors governing Fe availability in the shelf/near‐shelf region

AbstractThe California Current System is a productive eastern boundary region off the coasts of Washington, Oregon, and California. There is strong seasonality to the region, with high levels of rainfall and river input to the coastal ocean during the winter season, and coastal and Ekman upwelling during the spring and summer. Iron (Fe) input to the coastal ocean during the winter months can be stored in the continental shelf mud belts and then be delivered to the surface ocean by upwelling in the spring and summer. There have been a number of studies providing strong evidence of Fe‐limitation of diatom growth occurring in regions of the California Current System off of California, and the occurrence of Fe‐limitation has been linked with narrow continental shelf mud belt width and low river input. We provide evidence for potential Fe‐limitation of diatoms off the southern coast of Oregon in July 2014, just off the shelf break near Cape Blanco in a region with moderate shelf width and river input. Since eastern boundary regions account for a disproportionally large amount of global primary production, this observation of potential Fe‐limitation in an unexpected near‐shore region of the California Current System has implications for global models of primary productivity. In order to re‐evaluate the factors impacting Fe availability, we utilize satellite imagery to compare with historical datasets, and show that unexpected levels of Fe can often be explained by eddies, plumes of upwelled water moving offshore, or lack of recent upwelling.

The lacustrine microbial carbonate factory of the successive Lake Bonneville and Great Salt Lake, Utah, USA

AbstractThe Bonneville Basin is a continental lacustrine system accommodating extensive microbial carbonate deposits corresponding to two distinct phases: the deep Lake Bonneville (30 000 to 11 500 14C bp) and the shallow Great Salt Lake (since 11 500 14C bp). A characterization of these microbial deposits and their associated sediments provides insights into their spatio‐temporal distribution patterns. The Bonneville phase preferentially displays vertical distribution of the microbial deposits resulting from high‐amplitude lake level variations. Due to the basin physiography, the microbial deposits were restricted to a narrow shoreline belt following Bonneville lake level variations. Carbonate production was more efficient during intervals of relative lake level stability as recorded by the formation of successive terraces. In contrast, the Great Salt Lake microbial deposits showed a great lateral distribution, linked to the modern flat bottom configuration. A low vertical distribution of the microbial deposits was the result of the shallow water depth combined with a low amplitude of lake level fluctuations. These younger microbial deposits display a higher diversity of fabrics and sizes. They are distributed along an extensive ‘shore to lake’ transect on a flat platform in relation to local and progressive accommodation space changes. Microbial deposits are temporally discontinuous throughout the lake history showing longer hiatuses during the Bonneville phase. The main parameters controlling the rate of carbonate production are related to the interaction between physical (kinetics of the mineral precipitation, lake water temperature and runoff), chemical (Ca2+, Mg2+ and HCO3− concentrations, Mg/Ca ratio, dilution and depletion) and/or biological (trophic) factors. The contrast in evolution of Lake Bonneville and Great Salt Lake microbial deposits during their lacustrine history leads to discussions on major chemical and climatic changes during this interval as well as the role of physiography. Furthermore, it provides novel insights into the composition, structure and formation of microbialite‐rich carbonate deposits under freshwater and hypersaline conditions.

Мониторингфауны мангровых посадок залива Дам Бай (О. Че, залив Ня-Чанг)

Monitoring of fauna in mangrove plantations is extremely important for understanding developmental patterns of mangrove ecosystems, which contributes to conservation, rehabilitation and sustinable management issues of this economically and ecologically valuable system. In Dam Bay on a mud flat fringed by narrow belt of Rhizophora apiculata, seedlings of the same species were planted in 2005 and 2009. Dynamics of species richness, species composition and density of macro invertebrate fauna were recorded in newly planted mangrove association during ten years. Comparison between the fauna of mangrove plantings at Dam Bay and natural association in Nha Phu Bay was conducted. For those purposes quantitative and qualitative samples were collected from year 2005 to 2015 for Dam Bay, and years 2012 and 2014 for Nha Phu. The most diverse groups of invertebrates were gastropods, bivalves and crabs in both natural and planted mangroves. Faunal richness and quantitative characteristics altered significantly during monitoring period in newly planted mangrove association. We recorded the growth of species richness and density of eurybiotic and opportunistic species, due to the enrichment of the sediments by organic matter and appearance of new hard substrata. At the beginning of 2008, we observed progressive colonization of the plantation by specialized mangrove species, the main reasons were the growth of young plants and as a result gradual complication of vegetation structure. Nevertheless even after 10 years the plantation has lower species richness of specialized fauna than the natural association in Nha Phu. The structure of fauna i.e. proportion of specialized versus eurybiotic species and their abundance may be used as indicators of condition of mangrove associations.

Phanerogamic flora and phytogeography of the Cloud Dwarf Forests of Ibitipoca State Park, Minas Gerais, Brazil

Abstract: This study was developed in Ibitipoca State Park (ISP), a mountainous massif that stands out in the Serra da Mantiqueira, in the Southeastern Region of Brazil. The vegetation is represented by a phytophysiognomic mosaic where areas of campos rupestres interspersed with cloud dwarf forests predominate, at altitudes of 1100 to 1700 m.s.m. The cloud dwarf forests exist in narrow altitude belts on the mountain peaks, immersed in a layer of clouds. They form a peculiar landscape high in the mountains by the short stature of the arboreal elements and richness of lichens and bryophytes, which develop under constant condensation of humidity, low temperatures, and frequent winds. The objective of the present work was to determine the floristic composition and phytogeography of the cloud dwarf forests of ISP. Twelve monthly campaigns were conducted to collect botanical material during the years 2014 and 2015. The collected material was deposited in the collection of the CESJ Herbarium. A total of 372 species, 209 genera, and 73 families of phanerogams were found. The richest families were Orchidaceae (84 spp.), Asteraceae (39 spp.), and Melastomataceae (21 spp). The genera with the greatest wealth were Leandra (09 spp.), Epidendrum (09 spp.), Pleurothallis (09 spp.), Mikania (07 spp.), and Miconia (07 spp). The arboreal habit was predominant with 103 species (27.7%), followed by 83 shrubs (22.3%), 82 epiphytic herbs (22%), 80 terrestrial herbs (21.5%), and 23 lianas (6.5%). The floristic composition presents elements typical of altitude vegetation, including species of campos rupestres and high epiphytes richness, especially of the families Orchidaceae and Bromeliaceae. The genera with tropical distribution represent 86.5%, whereas the temperate elements represent 13.5% of the total. The cloud dwarf forests presented similarity, at the family and gender levels, with the upper montane forests of the Andes, besides phytogeographic characteristics that allow to associate them to a transition environment between the campos rupestres and the upper montane forests of the Southeast Region of Brazil.

Modeling and optimal control analysis of Zika virus with media impact

Zika virus disease is a mosquito-borne disease which is mainly transmitted by the female Aedes mosquitoes. Initially, since the 1950, the Zika virus disease (or Zika fever) was known to occur only in a narrow equatorial belt from Africa to Asia but from 2007 to 2016, the virus spread eastward (i.e. across the Pacific Ocean to the Americas) and that led to the 2015–2016 Zika virus epidemic. Now, it is creating a viral threat to societies all over the World because it spreads very fast in a globally connected world. The Zika virus is a member of the virus family Flaviviridae and its dynamics is governed by the day time activities of Aedes mosquitoes (i.e. A. aegypti and A. albopictus, etc.). However, there also exist new evidences of its transmission dynamics being governed via sexual contact and that has been reported from different nations (i.e. Argentina, Canada, Chile, France, Italy, New Zealand, Peru, Portugal, and USA). This paper introduces a mathematical model to investigate the transmission dynamics of Zika virus disease through the inclusion of the impact of media. Our proposed model involves both the possible routes of transmission (i.e. mosquito borne and sexual transmission). The existence and stability of different equilibria of this model are presented and analyzed in detail. The basic reproduction number $$R_0$$ of the model is computed and it is found that for $$R_0<1$$ , the disease free equilibrium of the model is locally asymptotically stable. When $$R_0>1$$ , the endemic equilibrium point exists and is locally asymptotically stable under some restriction on parameters. For $$R_0<1$$ , backward bifurcation occurs, which suggests that lowering $$R_0$$ below one is not enough to eliminate the disease from the population. Finally, we extend our model to optimal control model by introducing two types of control parameters and compare the results of both the models using numerical simulation. Our presented results highlight the efficacy of the role of media and show that the proposed model is efficient in the analysis of transmission dynamics of the Zika virus disease. The sensitivity analysis of the parameters suggests that the key parameters are the mosquito biting rate and the rate of transmission due to the sexual contact between human to human. A small increase in any of these parameters can lead to great increase in the basic reproduction number $$R_0$$ and this causes a large outbreak of this disease. So, the control policies should aim for controlling both the routes of transmission of this disease.

The Pico do Itapeva Formation: A record of gravitational flow deposits in an Ediacaran intracontinental basin, southern Brasília Orogen, SE Brazil

The Pico do Itapeva Formation is a key metasedimentary unit to the understanding of the extensional events that occurred between the late stage of the southern Brasília Orogen collision and the main collision in the central Ribeira Orogen. The formation crops out in a 20 km long NE-trending narrow belt in the Mantiqueira mountain range in eastern São Paulo State, Brazil. It is located in the interference zone of the southern Brasília and the central Ribeira orogens and records deformation and greenschist facies metamorphism (biotite zone) related to the Brasiliano orogeny. The Pico do Itapeva Formation rests unconformably on a metaigneous substratum of the Socorro-Guaxupé Nappe/Embu Terrane and, on the southern side, is truncated by a steep SE-dipping dextral reverse shear zone. It consists of a coarsening- and thickening-upward succession, with minimum thickness of 800 m, composed of lutite, arkose and conglomerate. These rocks constitute three distinct lithofacies associations: LAI- arkose, arkose-lutite composite beds, lutite and fine conglomerate beds; LAII- arkose, pebbly arkose and scarce lutite and; LAIII- conglomerate and pebbly arkose. Most of the beds are massive; graded beds, dish and convolute structures occur locally. Bed thickness varies from thin to very thick and amalgamated bodies constitute up to 30m thick strata. Three mappable units at scale 1:20,000 were recognized based on different proportions of the three lithofacies associations. The deposits are interpreted as the record of mass flows and associated processes in a fan delta setting developed in an intermontane rift basin. U-Pb LA-ICP-MS detrital zircon ages suggest the maximum depositional age at ca. 611 Ma and the basin evolution is interpreted in the range between 611 and 580 Ma during an inter-orogenic stage between the Brasília and Ribeira orogenies.

Spatial coincidence and similar geochemistry of Late Triassic and Eocene–Oligocene magmatism in the Andes of northern Chile: evidence from the MMH porphyry type Cu–Mo deposit, Chuquicamata District

The MMH porphyry type copper–molybdenum deposit in northern Chile is the newest mine in the Chuquicamata District, one of largest copper concentrations on Earth. Mineralized Eocene–Oligocene porphyry intrusions are hosted by essentially barren Triassic granodiorites. Despite a century of exploitation, geologists still have problems in the mine distinguishing the Triassic granodiorite from the most important ore-carrying Eocene porphyries in the district. To resolve the problem, internally consistent high-quality geochemical analyses of the Triassic and Tertiary intrusives were carried out: explaining the confusion, they show that the rock units in question are nearly identical in composition and thus respond equally to hydrothermal alteration. In detail, the only difference in terms of chemical composition is that the main Eocene–Oligocene porphyries carry relatively less Fe and Ni. Unexpectedly, the mineralized Eocene–Oligocene porphyries have consistently less U and Th than other Tertiary intrusions in the district, a characteristic that may be valuable in exploration. The supergiant copper–molybdenum deposits in the Central Andes were formed within a narrow interval between 45 and 31 Ma, close to 7% of the 200 My duration of “Andean” magmatism, which resulted from subduction of oceanic lithosphere under South America since the Jurassic. Although recent work has shown that subduction was active on the margin since Paleozoic times, pre-Andean (pre-Jurassic) “Gondwanan” magmatism is often described as being very different, having involved crustal melting and the generation of massive peraluminous rhyolites and granites. This study shows that the indistinguishable Late Triassic and Eocene–Oligocene intrusions occupy the same narrow NS geographic belt in northern Chile. If it is accepted that magma character may determine the potential to generate economic Cu–Mo deposits, then Late Triassic volcano-plutonic centres in the same location in the South American margin could have contained valuable ore deposits, although their preservation will depend on the level attained by pre-mid Jurassic erosion. Both Late Triassic and Eocene–Oligocene magmatic events occurred during the waning stages of vigorous volcano-plutonic cycles, and both preceded apparent gaps in igneous activity (Rhaetian and post-Oligocene), abrupt lateral shifts of the volcanic front and radical changes in the character of the magmas generated. Both Late Triassic and Eocene–Oligocene intrusions were emplaced along the same narrow strip of crust; it is probable that they both exploited the same deep crustal structures. The Eocene–Oligocene magmatic front was controlled by an orogen-parallel shear system caused by oblique subduction; it is possible that Late Triassic magmatism along the same belt had a similar setting. The identified Rhaetian gap in subduction and magmatism may have widespread implications.

The origin of Late Ediacaran post-collisional granites near the Chad Lineament, Saharan Metacraton, South-Central Chad

The southern Saharan Metacraton is one of the least geologically constrained regions in the world as bedrock exposures are rare. To the west of Lake Fitri near the communities of Ngoura and Moyto in south-central Chad there are two granitic inliers that form a series of lenticular to ellipsoidal low laying hills. Very little is known about the Lake Fitri inliers and their regional correlation to larger massifs in Chad is undetermined. The granites yielded weighted-mean zircon 206Pb/238U ages of 554 ± 8 Ma and 546 ± 8 Ma indicating they were emplaced ~45 million years after the cessation of arc-related magmatism and the subsequent collision between the Congo-São Francisco Craton and the Saharan Metacraton. The rocks have distinct groupings of inherited zircons with ages of ~580 Ma and ~635 Ma suggesting they are at least in part derived by recycling of older crustal rocks. The biotite mineral chemistry, whole rock compositions and petrological modeling indicate the granites were derived by melting of crustal lithologies but the whole rock Nd isotopes (εNd(t) = +1.3–+2.9) are characteristic of a mantle source. The contrasting inheritance-rich nature of the granites with a juvenile Nd isotopic signature is likely due to mixing between magmas derived from juvenile (Neoproterozoic) arc-related crust and asthenospheric magmas. Asthenospheric upwelling was probably a response to post-orogenic lithospheric delamination related to fault movement along the Chad Lineament, a possible extension of the Tcholliré-Banyo shear zone that extended to the interior of the Saharan Metacraton. The implications are that lithospheric delamination may not have occurred immediately after collision but rather propagated along a narrow belt that extended well into the central regions of the Saharan Metacraton.

Epidemiologic review of zika virus disease

Zika virus disease has resonated great concern globally. The World Health Organization declared it “a public health emergency of International concern” on 1st February, 2016. The recent outbreaks have become a major challenge due to a drift from its earlier known benign exanthematous spectrum to a causal link to microcephaly. Historically, the name Zika virus comes from the Zika Forest of Uganda. It was first identified in 1947 among Rhesus Macaque sub-population. Two genetically distinct isolates have been well characterized; the Asian and African strains. This virus is spread by bites of day-time-active Aedes mosquitoes; the Aedes aegypti and Aedes albopictus. Zika Virus appears to spread along a narrow equatorial belt of Africa to Asia through the Pacific Ocean to French Polynesia, New Caledonia (southwest Pacific Ocean), the Cook Islands (south Pacific), and Easter Island (a Chilean territory in Polynesia), and most recently to Mexico, Central America, the Caribbean, and South America, where today has assumed a pandemic proportion.Up to eighty percent of infections are asymptomatic. Symptomatic infections are characterized by a self-limiting febrile illness and maculopapular rash, arthralgia, conjunctivitis, back pain and mild headaches. Maternal Zika viral load is thought to be a significant risk factor to fetal infection leading to invasion of either trophoblasts or placental cells or both through maternal decidua. Zika viral RNA proteins and associated extensive selective tissue injuries have been demonstrated in the brains and spinal cords of abortuses. Diagnosis of Zika virus is essentially based on viral RNA detection from clinical specimens. Currently, licensed preventive medicines or vaccines are unavailable. With the wide spate of recent outbreaks and consequent neurologic morbidity and mortality, there is need for deployment of point-of-care equipment for screening of pregnant women in our environment. This is an ambitious call for advocacy by all relevant health care providers.Keywords: Zika Virus, disease outbreaks, microcephaly, Aedes mosquitoes

Analysis of the Herschel DEBRIS Sun-like star sample

This paper presents a study of circumstellar debris around Sun-like stars using data from the Herschel DEBRIS Key Programme. DEBRIS is an unbiased survey comprising the nearest ~90 stars of each spectral type A-M. Analysis of the 275 F-K stars shows that excess emission from a debris disc was detected around 47 stars, giving a detection rate of 17.1+2.6-2.3 per cent, with lower rates for later spectral types. For each target a blackbody spectrum was fitted to the dust emission to determine its fractional luminosity and temperature. The derived under- lying distribution of fractional luminosity versus blackbody radius in the population showed that most detected discs are concentrated at f ~ 10^-5 and at temperatures corresponding to blackbody radii 7-40 AU, which scales to ~40 AU for realistic dust properties (similar to the current Kuiper belt). Two outlying populations are also evident; five stars have exceptionally bright emission ( f > 5x10^-5), and one has unusually hot dust < 4 AU. The excess emission distributions at all wavelengths were fitted with a steady-state evolution model, showing these are compatible with all stars being born with a narrow belt that then undergoes collisional grinding. However, the model cannot explain the hot dust systems - likely originating in transient events - and bright emission systems - arising potentially from atypically massive discs or recent stirring. The emission from the present-day Kuiper belt is predicted to be close to the median of the population, suggesting that half of stars have either depleted their Kuiper belts (similar to the Solar System), or had a lower planetesimal formation efficiency.

The early Miocene flora of Güvem (Central Anatolia, Turkey): a window into early Neogene vegetation and environments in the Eastern Mediterranean

AbstractThe early Burdigalian (MN3) plant assemblage of the Güvem area (northwestern Central Anatolia) is preserved in lacustrine sediments of the Dereköy pyroclastics. Its age is well constrained by radiometric dates of basaltic rocks bracketing the pyroclastics, making the Güvem flora one of the extremely few precisely dated early Miocene floras in the Mediterranean region. The rich assemblage of impression fossils comprises ferns and fern allies (2 species), gymnosperms (12 spp.) and angiosperms (129 spp.).Ilex miodipyrenasp. nov. is described as a new fossil-species. The most diverse families in the assemblage are the Fagaceae with 12 taxa and the Fabaceae with 12 leaf morphotypes and one fruit taxon. Aquatic plants are represented by seven taxa, riparian (including palms) and swamp forest elements by &gt;35 taxa, and lianas by three taxa (Smilaxspp.,Chaneya). The relatively large number of aquatic and riparian/swamp elements is congruent with the rich fish, amphibian and reptile record of the Güvem area. Another characteristic feature of the plant assemblage is the presence of various lobed leaves which show similarities with modern species of different families (e.g.Alangium, various Malvales). Trees and shrubs growing on well-drained soils and forming closed-canopy and open-canopy forests are the most diversified group (&gt;70 taxa). In terms of number of specimens in the collection and based on field observations, by far the most abundant leaf fossils belong to evergreen oaks ofQuercus drymejaandQ. mediterraneaand to various types of foliage that cannot be assigned to a particular extant or extinct genus of Fagaceae. These sclerophyllous trees must have covered vast areas surrounding the wetlands that developed during the early Miocene in the Güvem Basin. Based on a recent reassessment of the ecology and taxonomic affinity of these trees, they are considered to reflect humid temperate climatic conditions but with a brief drier season during the winter months. These forests are more similar to the laurel forests of the southeastern United States and those stretching in a narrow belt south of the Himalayas to eastern central China. The large number of Fabaceae may indicate the presence of warm subtropical environments but this is difficult to assess, as they are known for having wide ecological ranges today and in the past. All in all, a larger part of the plant taxa point to forested vegetation. This is in agreement with previous palynological studies which detected only small amounts of herbaceous and grass pollen. Open patches of vegetation may have been restricted to river banks and to rocky areas in a volcanic landscape. The biogeographic patterns detected for the early Miocene of the Güvem assemblage are manifold; most taxa are widespread Northern Hemispheric elements. A substantial part of the species migrated from Asia into Europe during the (late) Paleogene and reached Anatolia during the early Miocene (Fagus,Paliurus,Chaneya,Ailanthus,Quercus kubinyii,Davallia haidingeri,Acer angustilobum,A. palaeosaccharinum). Fewer taxa may have been in Anatolia before they migrated to Europe (e.g.Nerium,Smilax miohavanensis,Quercus sosnowskyi). Finally, very few taxa are Anatolian endemics (e.g.Ilex miodipyrena).

South Flank of the Yangtze Delta: Past, present, and future

Chenier plain and mudflat development in the South Flank of the Yangtze Delta are examined by multi-disciplinary methods over different spatiotemporal scales and changing human-earth interactions. The study site contains a narrow belt of elongated ridge complexes that formed along the sediment-deficient open coast from 6500 to 4000yr BP. Since then and until the past two decades, shoreline progradation has accelerated due to increasing sediment supply, fueling rapid deltaic expansion. Superimposed on this trend are a series of discrete sand-dominated ridges deposited during several stormy intervals. Tidal flat development is regulated by complex estuarine processes. Short-term morphodynamic variations at the site are caused by the alternations of tides and waves, while intermediate morphodynamic variations are controlled by the multi-decadal shifting of river stem channel and stormy climates. The ongoing rapid accretion on the tidal flats is predicted to continue into the near future because the estuarine buffer effect is expected to balance the adverse impacts of decreasing riverine sediment discharge and rising sea level. Technological developments during the last ~2000years are exemplified by seawall construction against sea flooding, marking a transition from passive to active. Dike construction has been used more frequently and intensively to reclaim land since the 1970s, in support of the booming socioeconomic development in the region. Lessons from complex morphodynamic change and human-earth interactions in the Southern Yangtze Delta admonish us to not reclaim coastal wetland by lower-flat enclosures (constructing new dikes near the low waterline), while an optimal alternative would be to implement upper-flat enclosures (constructing new dikes around the high waterline) on the continuously accretionary tidal flats, with auxiliary biological restoration engineering, to satisfy both socioeconomic development and sustainable wetland conservancy.

Anomalous heat flow belt along the continental margin of Brazil

A comprehensive analysis of thermal gradient and heat flow data was carried out for sedimentary basins situated in the continental margin of Brazil (CMB). The results point to the existence of a narrow belt within CMB, where temperature gradients are higher than 30 °C/km and the heat flow is in excess of 70 mW/m2. This anomalous geothermal belt is confined between zones of relatively low to normal heat flow in the adjacent continental and oceanic regions. The width of the belt is somewhat variable, but most of it falls within the range of 100–300 km. The spatial extent is relatively large in the southern (in the basins of Pelotas, Santos and Campos) and northern (in the basins of Potiguar and Ceara) parts, when compared with those in the central parts (in the basins of South Bahia, Sergipe and Alagoas). The characteristics of heat flow anomalies appear to be compatible with those produced by thermal sources at depths in the lower crust. Hence, magma emplacement at the transition zone between lower crust and upper mantle is considered the likely mechanism producing such anomalies. Seismicity within the belt is relatively weak, with focal depths less than 10 km for most of the events. Such observations imply that “tectonic bonding” between continental and oceanic segments, at the transition zone of CMB, is relatively weak. Hence, it is proposed that passive margins like CMB be considered as constituting a type of plate boundary that is aseismic at sub-crustal levels, but allows for escape of significant amounts of earth’s internal heat at shallow depths.

Latest Miocene transtensional rifting of northeast Isla Tiburón, eastern margin of the Gulf of California

Details about the timing and kinematics of rifting are crucial to understand the conditions that led to strain localization, continental rupture, and formation of the Gulf of California ocean basin. We integrate detailed geologic and structural mapping, basin analysis, and geochronology to characterize transtensional rifting on northeastern Isla Tiburón, a proximal onshore exposure of the rifted North America margin, adjacent to the axis of the Gulf of California. Slip on the Kunkaak normal fault tilted its hanging wall down-to-the-east ~70° and formed the non-marine Tecomate basin, deposited across a ~20° angular unconformity. From 7.1–6.4Ma, the hanging wall tilted at 35±5°/Myr, while non-marine sandstone and conglomerate accumulated at 1.4±0.2mm/yr. At least 1.8±0.1km of sediments and pyroclastic deposits accumulated in the Tecomate basin concurrent with clockwise vertical-axis block rotation and ~2.8km of total dip-slip motion on the Kunkaak fault. Linear extrapolation of tilting and sedimentation rates suggests that faulting and basin deposition initiated ~7.6–7.4Ma, but an older history involving initially slower rates is permissible. The Kunkaak fault and Tecomate basin are truncated by NW-striking, dextral-oblique structures, including the Yawassag fault, which accrued >8km of post-6.4Ma dextral displacement. The Coastal Sonora fault zone on mainland Sonora, which accrued several tens of kilometers of late Miocene dextral offset, continues to the northwest, across northeastern Isla Tiburón and offshore into the Gulf of California. The establishment of rapid, latest Miocene transtension in the Coastal Sonora fault zone was synchronous with the 8–7Ma onset of transform faulting and basin formation along the nascent Pacific-North America plate boundary throughout northwestern Mexico and southern California. Plate boundary strain localized into this Gulf of California shear zone, a narrow transtensional belt that subsequently hosted the marine incursion and continental rupture in the Gulf of California.