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  • 1
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Ecology, Evolution, and Systematics 35 (2004), S. 523-556 
    ISSN: 1543-592X
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: The evolutionary succession of marine photoautotrophs began with the origin of photosynthesis in the Archean Eon, perhaps as early as 3.8 billion years ago. Since that time, Earth's atmosphere, continents, and oceans have undergone substantial cyclic and secular physical, chemical, and biological changes that selected for different phytoplankton taxa. Early in the history of eukaryotic algae, between 1.6 and 1.2 billion years ago, an evolutionary schism gave rise to "green" (chlorophyll b-containing) and "red" (chlorophyll c-containing) plastid groups. Members of the "green" plastid line were important constituents of Neoproterozoic and Paleozoic oceans, and, ultimately, one green clade colonized land. By the mid-Mesozoic, the green line had become ecologically less important in the oceans. In its place, three groups of chlorophyll c-containing eukaryotes, the dinoflagellates, coccolithophorids, and diatoms, began evolutionary trajectories that have culminated in ecological dominance in the contemporary oceans. Breakup of the supercontinent Pangea, continental shelf flooding, and changes in ocean redox chemistry may all have contributed to this evolutionary transition. At the same time, the evolution of these modern eukaryotic taxa has influenced both the structure of marine food webs and global biogeochemical cycles.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Earth and Planetary Sciences 27 (1999), S. 313-358 
    ISSN: 0084-6597
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Geosciences , Physics
    Notes: Abstract Stromatolites are attached, lithified sedimentary growth structures, accretionary away from a point or limited surface of initiation. Though the accretion process is commonly regarded to result from the sediment trapping or precipitation-inducing activities of microbial mats, little evidence of this process is preserved in most Precambrian stromatolites. The successful study and interpretation of stromatolites requires a process-based approach, oriented toward deconvolving the replacement textures of ancient stromatolites. The effects of diagenetic recrystallization first must be accounted for, followed by analysis of lamination textures and deduction of possible accretion mechanisms. Accretion hypotheses can be tested using numerical simulations based on modern stromatolite growth processes. Application of this approach has shown that stromatolites were originally formed largely through in situ precipitation of laminae during Archean and older Proterozoic times, but that younger Proterozoic stromatolites grew largely through the accretion of carbonate sediments, most likely through the physical process of microbial trapping and binding. This trend most likely reflects long-term evolution of the earth's environment rather than microbial communities.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 36 (1989), S. 0 
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Upper Proterozoic carbonate successions from central East Greenland (the Limestone-Dolomite ‘Series’ of the Eleonore Bay Group) and Svalbard (the Backlundtoppen Formation of the Akademikerbreen Group, Spitsbergen, and the Upper Russö Formation of the Raoldtoppen Group, Nordaustlandet) contain thick sequences dominated by pisolites. These rocks were generated in shallow marine enviroments, and the pisoids are essentially oversized ooids. A marine environment is supported by the thickness and lateral extent of the carbonates; by a sedimentary association of pisolites with stromatolites, flake-conglomerates, calcarenites, calcilutites, microphytolites, and ooids similar to that found in numerous other Proterozoic carbonate successions; by sedimentary structures, including cross-beds and megaripples that characterize the pisolitic beds; and by microfossils of endolithic cyanobacteria that are specifically comparable to microorganisms that inhabit modern marine ooids of the Bahama Banks. Petrographic features and strontium abundances suggest that the pisoids were originally aragonitic, but neomorphism, silicification, calcitization, and dolomitization have extensively modified original mineralogies and fabrics. The East Greenland and Svalbard pisolitic carbonates reflect similar depositional environments and diagenetic histories, reinforcing previous bio-, litho-, and chemostratigraphic interpretations that the two sequences accumulated contiguously in a coastal zone of pisoid genesis which extended for at least 600, and probably 1000 or more, kilometres.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Polar research 6 (1988), S. 0 
    ISSN: 1751-8369
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geography , Geosciences
    Notes: The stratigraphic importance of fossils is never more apparent than in attempts to unravel the complexities of metamorphic terrains. The age and stratigraphic relationships of the thick metasedimentary and metavolcanic succession of Prins Karls Forland, western Svalbard, have been the subject of investigation and debate since the early part of this century (Hoel 1914; Craig 1916; Tyrrel 1924), and sharply different interpretations have been proposed (e.g. Harland et al. 1979; Hjelle et al. 1979). Until now, such interpretations have been unconstrained by palaeontological data, an understandable consequence of the metamorphic alteration undergone by these rocks. In this paper, we report the discovery of stratigraphically useful microfossils preserved in chert nodules from carbonaceous, dolomitic shales on northern Prins Karls Forland. These fossils have significant implications for the stratigraphic and structural interpretation of Forland metasediments, as well as for the more general problem of palaeontological prospecting in severely deformed and metamorphosed terrains, including those characteristic of the Archean Eon.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 297 (1982), S. 57-60 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Organic-walled fossils of Proterozoic planktonic microorganisms are preserved in a wide variety of sedimentary rocks, ranging from lagoonal mudstones to distal turbiditic shales and greywackes. Microfossil assemblages can be correlated with sedimentary environments, permitting the palaeoecological ...
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 446 (2007), S. 661-663 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Phosphatized microfossils in the Ediacaran (635–542 Myr ago) Doushantuo Formation, south China, have been interpreted as the embryos of early animals. Despite experimental demonstration that embryos can be preserved, microstructural evidence that the Doushantuo remains are embryonic and ...
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The disappearance of iron formations from the geological record ∼1.8 billion years (Gyr) ago was the consequence of rising oxygen levels in the atmosphere starting 2.45–2.32 Gyr ago. It marks the end of a 2.5-Gyr period dominated by anoxic and iron-rich deep oceans. However, ...
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillian Magazines Ltd.
    Nature 423 (2003), S. 632-635 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Many independent lines of evidence document a large increase in the Earth's surface oxidation state 2,400 to 2,200 million years ago, and a second biospheric oxygenation 800 to 580 million years ago, just before large animals appear in the fossil record. Such a two-staged oxidation implies ...
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 375 (1995), S. 201-202 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] ON my first trip to London, 25 years ago, I chanced to see Ingrid Bergman in a West End production. She flubbed numerous lines; I was enchanted. It would have been hard not to be won over, because Bergman radiated an unmistakable delight in the encounter with play and audience, and joy in the ...
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  • 10
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 382 (1996), S. 111-112 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] THE fossil record shows a dramatic radiation in animal forms in the latest Protero-zoic and early Cambrian epochs, the so-called Cambrian Explosion. But molecular clock1'2 and developmental3 arguments instead favour much earlier splitting of invertebrate lineages. These differing results ...
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