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  • Cambridge University Press  (3)
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  • 1
    Publication Date: 2011-07-01
    Description: Abundant sulphur is present in the Late Miocene evaporitic sequence of the lacustrine Hellín basin in SE Spain. Weathering of Triassic evaporites controlled the chemical composition of the Miocene lake. The lacustrine deposits comprise gypsum, marlstones, diatomites and carbonate beds. Sulphur-bearing carbonate deposits predominantly consist of early diagenetic dolomite. Abundant dolomite crystals with a spheroidal habit are in accordance with an early formation and point to a microbial origin. The carbon isotopic composition of the dolomite (d13C values between -10 and -4‰) indicates mixing of lake water carbonate and carbonate derived from the remineralization of organic matter by heterotrophic bacteria. Dolomite precipitated syngenetically under evaporitic conditions as indicated by high oxygen isotope values (d18O between +6 and +11‰). Nodules of native sulphur are found in gypsum, carbonate beds and marlstone layers. Sulphur formed in the course of microbial sulphate reduction, as reflected by its strong depletion in 34S (d34S values as low as -17‰). Near to the surface many of the sulphur nodules were in part or completely substituted by secondary gypsum, which still reflects the sulphur isotopic composition of native sulphur (-18 to -10‰). This study exemplifies the role of bacterial sulphate reduction in the formation of dolomite and native sulphur in a semi-enclosed lacustrine basin during Late Miocene time.
    Print ISSN: 0016-7568
    Electronic ISSN: 1469-5081
    Topics: Geosciences
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  • 2
    Publication Date: 1989-05-01
    Description: A well-known tectonic event affecting the East Mediterranean region, generally referred to as ‘the’ Miocene–Pliocene phase, occurs at, or near the Miocene–Pliocene boundary. Recent sedimentological studies in Cyprus indicate that this ‘event’, in fact, is complex. The Tortonian–Lower Pliocene period is marked by a stress involving an N20 extension in the Polemi and Pissouri basins and by an N100 extension in the Psematismenos basin. Sedimentological studies have demonstrated three tectonic pulsations during Messinian time, prior to the Pliocene transgression. These are expressed by two episodes of seismic brecciation, and a palaeo-emersion is indicated by palaeosols and detrital discharges. These phenomena suggest brief tectonic instability during Messinian time. Microtectonic studies in the South Troodos basins of Cyprus reveal that the main change in tectonic stress does not coincide with the Miocene–Pliocene contact but occurs at the end of Lower Pliocene time. The authors conclude that the so-called Miocene–Pliocene ‘event’, in reality, is a series of subtle tectonic pulsations recorded clearly by sedimentary parameters.
    Print ISSN: 0016-7568
    Electronic ISSN: 1469-5081
    Topics: Geosciences
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  • 3
    Publication Date: 2011-02-17
    Description: Abundant sulphur is present in the Late Miocene evaporitic sequence of the lacustrine Hellín basin in SE Spain. Weathering of Triassic evaporites controlled the chemical composition of the Miocene lake. The lacustrine deposits comprise gypsum, marlstones, diatomites and carbonate beds. Sulphur-bearing carbonate deposits predominantly consist of early diagenetic dolomite. Abundant dolomite crystals with a spheroidal habit are in accordance with an early formation and point to a microbial origin. The carbon isotopic composition of the dolomite (δ13C values between −10 and −4‰) indicates mixing of lake water carbonate and carbonate derived from the remineralization of organic matter by heterotrophic bacteria. Dolomite precipitated syngenetically under evaporitic conditions as indicated by high oxygen isotope values (δ18O between +6 and +11‰). Nodules of native sulphur are found in gypsum, carbonate beds and marlstone layers. Sulphur formed in the course of microbial sulphate reduction, as reflected by its strong depletion in34S (δ34S values as low as −17‰). Near to the surface many of the sulphur nodules were in part or completely substituted by secondary gypsum, which still reflects the sulphur isotopic composition of native sulphur (−18 to −10‰). This study exemplifies the role of bacterial sulphate reduction in the formation of dolomite and native sulphur in a semi-enclosed lacustrine basin during Late Miocene time.
    Print ISSN: 0016-7568
    Electronic ISSN: 1469-5081
    Topics: Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
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