882 resultados para the Late Permian


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The number of well-dated pollen diagrams in Europe has increased considerably over the last 30 years and many of them have been submitted to the European Pollen Database (EPD). This allows for the construction of increasingly precise maps of Holocene vegetation change across the continent. Chronological information in the EPD has been expressed in uncalibrated radiocarbon years, and most chronologies to date are based on this time scale. Here we present new chronologies for most of the datasets stored in the EPD based on calibrated radiocarbon years. Age information associated with pollen diagrams is often derived from the pollen stratigraphy itself or from other sedimentological information. We reviewed these chronological tie points and assigned uncertainties to them. The steps taken to generate the new chronologies are described and the rationale for a new classification system for age uncertainties is introduced. The resulting chronologies are fit for most continental-scale questions. They may not provide the best age model for particular sites, but may be viewed as general purpose chronologies. Taxonomic particularities of the data stored in the EPD are explained. An example is given of how the database can be queried to select samples with appropriate age control as well as the suitable taxonomic level to answer a specific research question. © 2013 The Author(s).

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The Mfabeni peatland is the only known sub-tropical coastal fen that transcends the Last Glacial Maximum (LGM). This ca. 10m thick peat sequence provides a continuous sedimentation record spanning from the late Pleistocene to present (basal age c. 47kcalyr BP). We investigated the paleaeoenvironmental controls on peat formation and organic matter source input at the Mfabeni fen by: 1) exploring geochemical records (mass accumulation rate, total organic carbon, carbon accumulation rate, δC, δN and C/N ratio) to delineate primary production, organic matter source input, preservation and diagenetic processes, and 2) employ these geochemical signatures to reconstruct the palaeoenvironmental conditions and prevailing climate that drove carbon accumulation in the peatland. We established that the Mfabeni peat sediments have undergone minimal diagenetic alteration. The peat sequence was divided into 5 linear sedimentation rate (LSR) stages indicating distinct changes in climate and hydrological conditions: LSR stage 1 (c. 47 to c. 32.2kcalyr BP): predominantly cool and wet climate with C4 plant assemblages, interrupted by two short warming events. LSR stage 2 (c. 32.2 to c. 27.6kcalyr BP): dry and windy climate followed by a brief warm and wet period with increased C4 sedge swamp vegetation. LSR stage 3 (c. 27.6 to c. 20.3kcalyr BP): initial cool and wet period with prevailing C4 sedge plant assemblage until c. 23kcalyr BP; then an abrupt change to dry and cool glacial conditions and steady increases in C3 grasses. LSR stage 4 (c. 20.3 to c. 10.4kcalyr BP): continuation of cool and dry conditions and strong C3 grassland signature until c. 15kcalyr BP, after which precipitation increases. LSR stage 5 (c. 10.4kcalyr BP to present): characterised by extreme fluctuations between pervasive wet and warm to cool interglacial conditions with intermittent abrupt millennial-scale cooling/drying events and oscillations between C3 and C4 plant assemblages. In this study we reconstructed a high-resolution record of local hydrology, bulk plant assemblage and inferred climate since the Late Pleistocene, which suggest an anti-phase link between Southern African and the Northern Hemisphere, most notably during Heinrich (5 to 2) and Younger Dryas events. © 2013 Elsevier B.V.

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This paper aims to synthesize literature about the definition, prevalence, onset and treatments associated with late effects. A rapid review was conducted using Google Scholar to identify reviews related to the late effects of adult-onset cancers. Papers were included if they provided a definition of late effects and/or presented a review of late effects as a result of adult-onset cancers in patients aged 18 years or older. Reviews related to nonmelanoma skin cancer were excluded. Reviews focusing on late effects in survivors of childhood-onset cancers (younger than 18 years) were ineligible for inclusion in the review. A total of 16 reviews were identified. Between 0% and 100% of survivors experienced a range of physical, psychological and social late effects. The onset of physical late effects was defined broadly as 'months or years' after treatment, whereas psychological late effects were defined as occurring at the end of treatment or similarly to physical late effects as 'months or years' after treatment. Few reviews provided an operational definition of late effects, and the onset of late effects was not often reported. Thus, reviews may have included the acute and long-term effects of cancer treatment. Evidence regarding causes, prevalence, and onset was incomplete for many late effects. Understanding the cause and onset of late effects is important in order to provide timely interventions to reduce the risk of late effect development in cancer patients.

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Archaeological excavation has provided an alternative source of evidence for the development of the late medieval peasant house. It is argued that whilst there was a significant change in building techniques in the decades around 1200 with the adoption of ground-set timbers, the most important factor which led to the survival of houses was a fall in real wages during the thirteenth century. This encouraged peasants to repair existing buildings, rather than replace them with new ones. Alternative traditions of building are also investigated. Stone construction was adopted in a number of areas of England, but in spite of the durability of the material, few medieval peasant buildings of this type have survived in use because of the failure to use lime mortar. Decisions about whether to invest in a building’s renovation will depend on the capital initially expended upon it. This interpretation is considered against the data from the fifteenth century and found to conform satisfactorily. Its implications are considered for the period between 1200 and 1350. Data collected from archaeological excavations combined with the results of dendrochronology on a growing number of closely dated standing buildings suggest that there was a significant ‘cull’ of houses in the period after 1350 as new dwellings were constructed.

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Spectral gamma ray (SGR) logs are used as stratigraphic tools in correlation, sequence stratigraphy and most recently, in clastic successions as a proxy for changes in hinterland palaeoweathering. In this study we analyse the spectral gamma ray signal recorded in two boreholes that penetrated the carbonate and evaporate-dominated Permian–Triassic boundary (PTB) in the South Pars Gasfield (offshore Iran, Persian Gulf) in an attempt to analyse palaeoenvironmental changes from the upper Permian (Upper Dalan Formation) and lower Triassic (Lower Kangan Formation). The results are compared to lithological changes, total organic carbon (TOC) contents and published stable isotope (δ18O, δ13C) results. This work is the first to consider palaeoclimatic effects on SGR logs from a carbonate/evaporate succession. While Th/U ratios compare well to isotope data (and thus a change to less arid hinterland climates from the Late Permian to the Early Triassic), Th/K ratios do not, suggesting a control not related to hinterland weathering. Furthermore, elevated Th/U ratios in the Early Triassic could reflect a global drawdown in U, rather than a more humid episode in the sediment hinterlands, with coincident changes in TOC. Previous work that used spectral gamma ray data in siliciclastic successions as a palaeoclimate proxy may not apply in carbonate/evaporate sedimentary rocks.

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Since the late nineteenth-century works of criminologists Lombroso and Lacassagne, tattoos in Europe have been commonly associated with deviant bodies. Like many other studies of tattoos of non-indigenous origin, the locus of our research is the convict body. Given the corporeal emphasis of prison records, we argue that tattoos form a crucial part of the power dynamic. Tattoos in the carceral context embody an inherent paradox of their being a component in the reidentification of 'habitual criminals'. We argue that their presence can be regarded as an expression of convict agency: by the act of imprinting unique identifiers on their bodies, convicts boldly defied the official gaze, while equally their description in official records exacted power over the deviant body. Cursory findings show an alignment with other national studies; corporeal inscriptions in Ireland were more prevalent in men's prisons than women's and associated, however loosely, with certain occupations. For instance, maritime and military motifs find representation. Recidivists were more likely to have tattoos than first-time offenders; inscriptions were described as monotone, rudimentary in design and incorporated a limited range of impressions. Further to our argument that tattoos form an expression of convict defiance of prison authority, we have found an unusual idiosyncrasy in the convict record, that is, that the agency of photography, while undermined in general terms, was manipulated by prison officers.

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This book examines the first human colonization of Asia and particularly the tropical environments of Southeast Asia during the Upper Pleistocene. In studyexamining the unique character of the Asian archaeological record, it reassesses long-accepted propositions about the development of human ‘modernity.’ Ryan J. Rabett reveals an evolutionarily relationship between colonization, the challenges encountered during this process – especially in relation to climatic and environmental change – and the forms of behaviour that emerged. This book argues that human ‘modernity’ is not something achieved in the remote past in one part of the world, but rather is a diverse, flexible, responsive, and on-going process of adaptation, one that continues to this day.

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From 1989 to 1994 a series of papers outlined evidence for a brief episode of climate change from arid to humid, and then back to arid, during the Carnian Stage of the late Triassic. This time of climate change was compared to marine and terrestrial biotic changes, mainly extinction and then radiation of flora and fauna. Subsequently termed, albeit incorrectly, the Carnian Pluvial Event (CPE) by successive authors, interest in this episode of climatic change has increased steadily, with new evidence being published as well as several challenges to the theory. The exact nature of this humid episode, whether reflecting widespread precipitation or more local effects, as well as its ultimate cause remains equivocal. Bed-by-bed sampling of the Carnian in the Southern Alps (Dolomites), shows the episode began with a negative carbon isotope excursion that lasted for only part of one ammonoid zone (A. austriacum). However, that the Carnian Humid Episode represents a significantly longer period, both environmentally and biotically, is irrefutable. The evidence is strongest in the European, Middle East, Himalayan, North American and Japanese successions, but not always so clear in South America, Antarctica and Australia. The eruption of the Wrangellia Large Igneous Province and global warming (causing increased evaporation in the Tethyan and Panthalassic oceans) are suggested as causes for the humid episode.

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A special meeting of the Association was held as it was resolved that Chancellor Harper was requested to prepare a memoir of the late Chancellor De Saussure.

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Tese de doutoramento (co-tutela), Ciências Geofísicas e da Geoinformação (Geofísica), Université de Toulouse, Universidade de Lisboa, 2013