981 resultados para Terraces (Geology)
Resumo:
Offshore geology of Pakistan is characterized by active and passive continental margins. These continental margins show very unique features such as an active Makran subduction zone in the west and the Indus delta and a submarine fan in the east. The geology of these features of Pakistan EEZ is inadequately known. This is a major obstacle in exploring mineral resources. Detailed study of coastal and shelf geology is needed for better understanding of the geology of the area and comprehensive evolution of its non-living resource potential. An understanding of the geological events including tectonic movements, sedimentation processes and geochemical history that comprise the geological history is very important to help in identification and estimation of resources. In Pakistan EEZ applying the current technology and undertaking research work to understand the seafloor features and mineral deposits associated with it will be very fruitful.
Resumo:
The climatic development of the Mid to Late Quaternary (last 400,000 years) is characterised by fluctuation between glacial and interglacial periods leading to the present interglacial, the Holocene. In comparison to preceding periods it was believed the Holocene represented a time of relative climatic stability. However, recent work has shown that the Holocene can be divided into cooler periods such as the Little Ice Age alternating with time intervals where climatic conditions ameliorated i.e. Medieval Warm Period, Holocene Thermal Optimum and the present Modern Optimum. In addition, the Holocene is recognised as a period with increasing anthropogenic influence on the environment. Onshore records recording glacial/interglacial cycles as well as anthropogenic effects are limited. However, sites of sediment accumulation on the shallow continental shelf offer the potential to reconstruct these events. Such sites include tunnel valleys and low energy, depositional settings. In this study we interrogated the sediment stratigraphy at such sites in the North Sea and Irish Sea using traditional techniques, as well as novel applications of geotechnical data, to reconstruct the palaeoenvironmental record. Within the German North Sea sector a combination of core, seismic and in-situ Cone Penetration Testing (CPT) data was used to identify sedimentary units, place them within a morphological context, relate them to glacial or interglacial periods stratigraphically, and correlate them across the German North Sea. Subsequently, we were able to revise the Mid to Late Quaternary stratigraphy for the North Sea using this new and novel data. Similarly, Holocene environmental changes were investigated within the Irish Sea at a depositional site with active anthropogenic influence. The methods used included analyses on grain-size distribution, foraminifera, gamma spectrometry, AMS 14C and physical core logging. The investigation revealed a strong fluctuating climatic signal early in the areas history before anthropogenic influence affects the record through trawling.
Resumo:
Molecular data have converged on a consensus about the genus-level phylogeny of extant platyrrhine monkeys, but for most extinct taxa and certainly for those older than the Pleistocene we must rely upon morphological evidence from fossils. This raises the question as to how well anatomical data mirror molecular phylogenies and how best to deal with discrepancies between the molecular and morphological data as we seek to extend our phylogenies to the placement of fossil taxa. Here I present parsimony-based phylogenetic analyses of extant and fossil platyrrhines based on an anatomical dataset of 399 dental characters and osteological features of the cranium and postcranium. I sample 16 extant taxa (one from each platyrrhine genus) and 20 extinct taxa of platyrrhines. The tree structure is constrained with a "molecular scaffold" of extant species as implemented in maximum parsimony using PAUP with the molecular-based 'backbone' approach. The data set encompasses most of the known extinct species of platyrrhines, ranging in age from latest Oligocene (∼26 Ma) to the Recent. The tree is rooted with extant catarrhines, and Late Eocene and Early Oligocene African anthropoids. Among the more interesting patterns to emerge are: (1) known early platyrrhines from the Late Oligocene through Early Miocene (26-16.5Ma) represent only stem platyrrhine taxa; (2) representatives of the three living platyrrhine families first occur between 15.7 Ma and 13.5 Ma; and (3) recently extinct primates from the Greater Antilles (Cuba, Jamaica, Hispaniola) are sister to the clade of extant platyrrhines and may have diverged in the Early Miocene. It is probable that the crown platyrrhine clade did not originate before about 20-24 Ma, a conclusion consistent with the phylogenetic analysis of fossil taxa presented here and with recent molecular clock estimates. The following biogeographic scenario is consistent with the phylogenetic findings and climatic and geologic evidence: Tropical South America has been a center for platyrrhine diversification since platyrrhines arrived on the continent in the middle Cenozoic. Platyrrhines dispersed from tropical South America to Patagonia at ∼25-24 Ma via a "Paraná Portal" through eastern South America across a retreating Paranense Sea. Phylogenetic bracketing suggests Antillean primates arrived via a sweepstakes route or island chain from northern South America in the Early Miocene, not via a proposed land bridge or island chain (GAARlandia) in the Early Oligocene (∼34 Ma). Patagonian and Antillean platyrrhines went extinct without leaving living descendants, the former at the end of the Early Miocene and the latter within the past six thousand years. Molecular evidence suggests crown platyrrhines arrived in Central America by crossing an intermittent connection through the Isthmus of Panama at or after 3.5Ma. Any more ancient Central American primates, should they be discovered, are unlikely to have given rise to the extant Central American taxa in situ.
Resumo:
UV-fluorescence microscopy provides a powerful tool for the assessment of the coherence of pollen and organic-walled microfossil assemblages in situations where recycling or the intrusion of younger pollen is suspected. It also provides sensitive information about the thermal maturity of pollen, important for assessing whether material has been heated. Examples are given from the Palaeolithic sites at Barnham, Suffolk, UK; Stanton Harcourt, Oxfordshire, UK; High Lodge, Suffolk, UK; Niah Cave, Sarawak, Malaysian Borneo; and Holocene sites at Wadi Dana, Jordan; Milldale and Creswell, Derbyshire, UK; and Dooncarton Mountain, County Mayo, Republic of Ireland.
Resumo:
Throughout the last few decades, sulfate concentrations in streamwater have received considerable attention due to their dominant role in anthropogenic acidification of surface waters. The objectives of this study conducted in the Oldman River Basin in Alberta (Canada) were to determine the influence of geology, land use and anthropogenic activities on sources, concentrations and fluxes of riverine sulfate on a watershed scale. This was achieved by combining hydrological, chemical and isotopic techniques. Surface water samples were collected from the main stem and tributaries of the Oldman River on a monthly basis between December 2000 and March 2003 and analyzed for chemical and isotopic compositions. At a given sampling site, sulfate sources were primarily dependent on geology and did not vary with time or flow condition. With increasing flow distance a gradual shift from ?34S values > 10 ‰ and ?18O values > 0 ‰ of riverine sulfate indicating evaporite dissolution and soil-derived sulfate in the predominantly forested headwaters, to negative ?34S and ?18O values suggested that sulfide oxidation was the predominant sulfate source in the agriculturally used downstream part of the watershed. Significant increases in sulfate concentrations and fluxes with downstream distance were observed, and were attributed to anthropogenically enhanced sulfide oxidation due to the presence of an extensive irrigation drainage network with seasonally varying water levels. Sulfate-S exports in an artificially drained subbasin (64 kg S/ha/yr) were found to exceed those in a naturally drained subbasin (4 kg S/ha/yr) by an order of magnitude. Our dataset suggests that the naturally occurring process of sulfide oxidation has been enhanced in the Oldman River Basin by the presence of an extensive network of drainage and irrigation canals.
Resumo:
The illegal burial of waste often occurs in locations where loose, transferable material is abundant, allowing covert pits to be dug or filled. The transfer of waste material onto suspects and their vehicles during loading, unloading, and burial is common, as is the case during other criminal activities such as the burial of murder victims. We use two case studies to show that the established principles of using geological materials in excluding or linking suspects can be applied to illegal waste disposal. In the first case, the layering of different geological materials on the tailgate of a container used to transport toxic waste demonstrated where the vehicle had been and denied the owner's alibi, associating him with an illegal dumpsite. In the second case, an unusual suite of minerals, recovered from a suspect's trousers, provided the intelligence that led environmental law enforcement officers to an illegal waste burial site.
Resumo:
Despite the compelling parallels between George Sand’s Laura; ou, le voyage dans le cristal and Jules Verne’s Voyage au centre de la Terre (both 1864), Sand’s place within the intertextual fabric of Verne’s novel has been occluded. By shifing the terms of the debate away from the vexed issues of borrowing, influence, or inspiration, and focusing on Verne’s sustained engagement with Sand’s work as a specifically geological fiction, this article sheds new light on the imbrication of the scientific and the fictional in Voyage au centre de la Terre, whereby geological and palaeontological references not only guarantee the text’s verisimilitude and underwrite its didactic objectives, but also fulfil an important metatextual function.