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Visar resultat 1 - 5 av 16 avhandlingar som matchar ovanstående sökkriterier.

  1. 1. Phosphate and Arsenic Cycling under Experimental Early Proterozoic Marine Conditions

    Författare :Christoffer Hemmingsson; Iain Pitcairn; Ernest Chi Fru; Per Andersson; Christophe Dupraz; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; DIP; Early Proterozoic; coprecipitation; adsorption; Iron formations; BIF; geokemi; Geochemistry;

    Sammanfattning : Nutrient dynamics in the Archean-Paleoproterozoic oceans strongly influenced primary productivity and the rise of atmospheric O2. Reconstructing the cycling of key nutrients such as dissolved inorganic phosphate (DIP) at this time is important for our understanding of the timing, rate and extent of atmospheric oxygenation at this time. LÄS MER

  3. 2. Palaeobiology and taphonomy of early problematic fossils

    Författare :Mónika Marti Mus; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Earth sciences; Geovetenskap; Earth sciences; Geovetenskap; Historical Geology and Paleontology; Historisk geologi och paleontologi;

    Sammanfattning : Extinct organisms that cannot be accommodated in any extant phylum are generally referred to as "problematic fossils". They are more numerous in progressively older strata and constitute an important part of the late Proterozoic and early Palaeozoic biota. LÄS MER

  4. 3. Isotopic studies of two early Proterozoic sulphide ores in the Bergslagen district, south-central Sweden

    Författare :Kjell Billström; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

    Sammanfattning : Two sulphide ores in Beraslaqen (Svärdsio and Ammeberq), south-central Sweden, have been examined for their isotope characteristics in order to elucidate their qenetic oriqin. The obtained isotopic data point to a common volcanic-exhalative mode of formation in aqreement with recent qeochemical data. LÄS MER

  5. 4. Palaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes

    Författare :Heda Agić; Małgorzata Moczydłowska; Shuhai Xiao; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; microfossils; eukaryotes; Mesoproterozoic; Neoproterozoic; Cambrian; Ordovician; palaeobiology; biostratigraphy; phylogeny; China; Estonia; Siberian Platform; prasinophytes; microstructure; Raman spectroscopy; Earth Science with specialization in Historical Geology and Palaeontology; Geovetenskap med inriktning mot historisk geologi och paleontologi;

    Sammanfattning : One of the most important events in the history of life is the evolution of the complex, eukaryotic cell. The eukaryotes are complex organisms with membrane-bound intracellular structures, and they include a variety of both single-celled and multicellular organisms: plants, animals, fungi and various protists. LÄS MER

  7. 5. Single fluid inclusion analysis using ToF-SIMS : Implications for ancient Earth biodiversiy and paleoenvironment studies

    Författare :Sandra Siljeström; Jukka Lausmaa; Andrew Steele; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; ToF-SIMS; time-of-flight secondary ion mass spectrometry; fluid inclusions; biomarkers; hopanes; steranes; early life; paleoenvironment; oil; eukaryotes; Earth sciences; Geovetenskap; geokemi; Geochemistry;

    Sammanfattning : When and how life first emerged on the Earth is an area of intense research. Signs of the first life on Earth, including morphological fossils, are scarce and hard to interpret. An alternative approach is to study organic biomarkers, which are molecular fossils commonly considered as bona fide biosignatures. LÄS MER