184 resultados para I.3.6 [Computer Graphics]: Methodology and Techniques

em Publishing Network for Geoscientific


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Understanding the evolution of Arctic polar climate from the protracted warmth of the middle Pliocene into the earliest glacial cycles in the Northern Hemisphere has been hindered by the lack of continuous, highly resolved Arctic time series. Evidence from Lake El'gygytgyn, NE Arctic Russia, shows that 3.6-3.4 million years ago, summer temperatures were ~8°C warmer than today when pCO2 was ~400 ppm. Multiproxy evidence suggests extreme warmth and polar amplification during the middle Pliocene, sudden stepped cooling events during the Pliocene-Pleistocene transition, and warmer than present Arctic summers until ~2.2 Ma, after the onset of Northern Hemispheric glaciation. Our data are consistent with sea-level records and other proxies indicating that Arctic cooling was insufficient to support large-scale ice sheets until the early Pleistocene.

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Seventy four samples of DSDP recovered cherts of Jurassic to Miocene age from varying locations, and 27 samples of on-land exposed cherts were analyzed for the isotopic composition of their oxygen and hydrogen. These studies were accompanied by mineralogical analyses and some isotopic analyses of the coexisting carbonates. d18O of chert ranges between 27 and 39%. relative to SMOW, d18O of porcellanite - between 30 and 42%. The consistent enrichment of opal-CT in porcellanites in 18O with respect to coexisting microcrystalline quartz in chert is probably a reflection of a different temperature (depth) of diagenesis of the two phases. d18O of deep sea cherts generally decrease with increasing age, indicating an overall cpoling of the ocean bottom during the last 150 m.y. A comparison of this trend with that recorded by benthonic foraminifera (Douglas and Savin, 1975; http://www.deepseadrilling.org/32/volume/dsdp32_15.pdf) indicates the possibility of d18O in deep sea cherts not being frozen in until several tens of millions of years after deposition. Cherts of any Age show a spread of d18O values, increasing diagenesis being reflected in a lowering of d18O. Drusy quartz has the lowest d18O values. On-land exposed cherts are consistently depleted in 18O in comparison to their deep sea time equivalent cherts. Water extracted from deep sea cherts ranges between 0.5 and 1.4 wt %. dD of this water ranges between -78 and -95%. and is not a function of d18O of the cherts (or the temperature of their formation).

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The analysis of time-dependent data is an important problem in many application domains, and interactive visualization of time-series data can help in understanding patterns in large time series data. Many effective approaches already exist for visual analysis of univariate time series supporting tasks such as assessment of data quality, detection of outliers, or identification of periodically or frequently occurring patterns. However, much fewer approaches exist which support multivariate time series. The existence of multiple values per time stamp makes the analysis task per se harder, and existing visualization techniques often do not scale well. We introduce an approach for visual analysis of large multivariate time-dependent data, based on the idea of projecting multivariate measurements to a 2D display, visualizing the time dimension by trajectories. We use visual data aggregation metaphors based on grouping of similar data elements to scale with multivariate time series. Aggregation procedures can either be based on statistical properties of the data or on data clustering routines. Appropriately defined user controls allow to navigate and explore the data and interactively steer the parameters of the data aggregation to enhance data analysis. We present an implementation of our approach and apply it on a comprehensive data set from the field of earth bservation, demonstrating the applicability and usefulness of our approach.

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New data on phosphorites collected by dredging and trawling at depths from 2700 to 520 m in the open Atlantic Ocean (i.e. outside of the shelf and the continental slope) are reported. Aphanitic, granular, brecciated, and conglomerate-like types are distinguished among the phosphorites. A comparison of the studied phosphorites with ones from the Atlantic shelf of Africa and from seamounts of other oceans is made.