Wyniki wyszukiwania - Biblioteka Nauki

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Structure and Phanerozoic evolution of the SW edge of the East European Craton in Poland - new insight from high-effort seismic reflection data (project PolandSPAN)

100%

Krzywiec P. , Malinowski M. , Mazur S. , Buffenmyer V. , Lewandowski M.

Geologia Sudetica

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2014

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tom Vol. 42

46--48

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Why are variations in bromine isotope compositions in the Earth's history larger than chlorine isotope compositions?

100%

Eggenkamp H.

Annales Universitatis Mariae Curie-Skłodowska, sectio AAA – Physica

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2015

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tom 70

EN

In this paper we discuss the marked discrepancy in global chlorine and bromine isotope variations. While, based on experimentally and theoretically determined fractionation factors, it is expected that bromine isotope variations should be, depending on the process, 2 to 7 times less than chlorine isotope variations it is observed that in formation brines the isotope variations of bromine are at least of the same size as chlorine isotope variations, and regularly even larger. In this paper we argue that this is caused by the fact that oxidation-reduction processes play a more important role in bromine isotope geochemistry than in chlorine isotope geochemistry. Due to the fact that the bromide ion is more easily to oxidise than the chloride ion Rayleigh effects can cause the observed larger variations in bromine isotope geochemistry. In this paper we propose that biochemical reactions (oxidation of bromide ions to methyl bromide) may be the major cause for this effect. Although we do not yet understand the full processes that take place we show that oxidation-reduction processes must be the main effect to explain the differences between the two isotope systems and propose that more research is developed to understand how the processes cause the observed variations.

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Materia magnetyczna na granicach stratygraficznych fanerozoiku

75%

Zalewski F.

Prace Naukowe Instytutu Nafty i Gazu

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2016

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tom nr 209 wyd. konferencyjne

119--122

EN

Today, the origin of spherules (spheroids) is attributed to two sources: anthropogenic (industrial) and/or cosmic. Anthropogenic spherules are produced in an industrial processes such as metallurgy, welding, grinding. Before the rise of industry and the use of iron tools we can find only spherules of cosmic origin deposited in the sediments. Spherules of cosmic origin fall to the surface of the Earth all the time [2]. They are a product of the process of ablation and combustion of meteoroids and cosmic dust during their fall through the Earth’s atmosphere, leaving behind a bolid trail [8]. Another natural source of origin of these objects are explosions. After passage of an extra-terrestrial body through the atmosphere, it hits the surface of the planet causing explosions. A big part of rock from the ground and extra-terrestrial matter evaporates during those explosions. The rest of the ejected material falls on the surface of the planet in the form of lumps, spherules, breccia, etc., covering a large area around the epicentre of the outbreak, or the entire planet. It forms a thin layer of molten post-explosive residue, which with the passing time – measured in geological terms – is covered with subsequent layers of sediment and becomes a timestamp in these sediments. Concentration of this type of material indicates a regional or global catastrophe caused by falling of objects of cosmic origin on Earth. One of these events was a meteorite fall in the area of the Yucatan Peninsula. This event caused an effect of nuclear winter and extinction of a large number of species of plants and animals, which left a layer of sediment enriched in iridium around the globe. This layer containing iridium and spherules is considered a typical strato border between the Cretaceous and Paleogene (K-T boundary) sediments, dating back to 66 million years [1, 11]. Tests to detect the magnetic spherules and matter on the borders of lithostratigraphic have been taken in the course of shale gas explorations in Poland. Previous research of laboratory samples from five wells indicate that material of the cosmic origin in the form of spherules and magnetic material is present in a large number of geological period borders, epochs and some stratigraphic formations. These results, combined with literature reports [5, 9] indicate the prevalence of the magnetic matter and spherules on the lithostratigraphic borders, which in turn creates the possibility of using the presence of that matter to a faster (compared to the current methods) and more precise determination of the relevant, lithostratigraphic borders.

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Fossil insects in Gondwana - localities and palaeodiversity trends

75%

Schluter T.

Acta Zoologica Cracoviensia

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2003

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tom 46

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nr Suppl.

EN

The faunal history of insects in the various fragments of Gondwana is presented. The first part of the paper summarizes the current knowledge of its insect-bearing localities, particularly their stratigraphy and fossil content, emphasizing the record of the higher systematic groups. The second part discusses some trends of their palaeobiodiversity as evidenced from the above mentioned sites. Generally, the knowledge of the fossil Gondwanan insect faunae is still much lower than that of the Laurasian ones, but has considerably increased over the last decade. Altogether about 85 localities are known from Gondwana, with a maximum of sites in Permian and a minimum in Jurassic times. Best represented is South America. Fossil insects of Gondwana are probably less known than those of Laurasia due to inadequate exploration rather than unfavourable conditions for the formation of deposits.

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The challenge of reconstructing the Phanerozoic sea level and the Pacific Basin tectonics

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Ruban D. A. , Conrad C. P. , Loon A. J. T.

Geologos

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2010

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tom Vol. 16, No. 4

235--243

EN

The relationships between the interior dynamics of our planet and global sea level can be unravelled when plate-tectonic reconstructions are available for the entire Earth. A review of global tectonics reveals significant deficiencies in our understanding of the geodynamic evolution of the Pacific (Panthalassa or Proto-Pacific) during the Cambrian-Jurassic time-span. This particular, but major, shortcoming presents a true challenge for modern geoscientists, who are encouraged to produce a detailed plate-tectonic reconstruction of the Pacific for the pre-Cretaceous in order to advance our understanding of Phanerozoic sea-level change. A set of approaches, including geological/geophysical modelling, investigation of accretionary prisms, palaeobiogeographical studies, and careful examination of eustatic sea-level changes, are proposed that will help geoscientists tackle the challenge of understanding how Pacific geodynamics affected global sea level during the Phanerozoic.